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## Photodiodes
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DSD2
FDS10X10
FDG05
FGAP71
FGA01
FGA01FC
FDG03
FGA21
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## Features
Thorlabs stocks a wide selection of discrete PIN junction photodiodes (PD) in various active area sizes and packages. These include
Our fastest photodiodes are the FDS015, FDS02, and FDS025 Si photodiodes. The FDS015 Si photodiode has a 35 ps rise time and a 0.65 pF junction capacitance, making it the highest speed, lowest capacitance photodiode offered below. Alternatively, the FD11A Si photodiode has a dark current of 2 pA, making it our photodiode with the lowest dark current. The FGAP71, a GaP photodiode, is useful for detection of UV light sources from 150 to 550 nm. The FD10D and FD05D are InGaAs photodiodes with high responsivity from 800 to 2600 nm, allowing detection of wavelengths beyond the normal 1800 nm range of typical InGaAs photodiodes. The DSD2 is a dual-band photodiode, which incorporates two photodetectors sandwiched on top of each other (Si substrate on top of an InGaAs substrate), offering a combined wavelength range of 400 to 1700 nm.
To complement our photodiode product line, we offer
For information on the photodiode saturation limit and the noise floor, as well as a collection of Thorlabs-conducted experiments regarding spatial uniformity (or varying responsivity) and dark current as a function of temperature, refer to the
Inhomogeneity on the edge of an active area of the detector can generate unwanted capacitance and resistance that distorts the time-domain response of a photodiode. Thorlabs therefore recommends that the incident light on the photodiode is well centered on the active area. This can be accomplished by placing a
Thorlabs offers spectral-flattening filters that are designed to improve the response uniformity of our silicon photodiodes. Click
The responsivity of a particular photodiode varies from lot to lot. Due to this, the photodiode you receive may have a slightly different response than what is represented below. For example, to the right, a graph for the FDS1010 photodiode shows the extent that the response may vary. This data was collected from 104 photodiodes. Minimum, Average, and Maximum responsivity was calculated at each data point and has been plotted.
To view typical responsivity vs. wavelength data for each individual photodiode, please click the
## Photodiode Tutorial
## Theory of Operation
A junction photodiode is an intrinsic device that behaves similarly to an ordinary signal diode, but it generates a photocurrent when light is absorbed in the depleted region of the junction semiconductor. A photodiode is a fast, highly linear device that exhibits high quantum efficiency based upon the application and may be used in a variety of different applications.
It is necessary to be able to correctly determine the level of the output current to expect and the responsivity based upon the incident light. Depicted in Figure 1 is a junction photodiode model with basic discrete components to help visualize the main characteristics and gain a better understanding of the operation of Thorlabs' photodiodes.
## Photodiode Terminology
The dark current present is also affected by the photodiode material and the size of the active area. Silicon devices generally produce low dark current compared to germanium devices which have high dark currents. The table below lists several photodiode materials and their relative dark currents, speeds, sensitivity, and costs.
Here, S/N is the Signal to Noise Ratio, Δf is the Noise Bandwidth, and Incident Energy has units of W/cm
Depending on the type of the photodiode, load resistance can affect the response speed. For maximum bandwidth, we recommend using a 50 Ω coaxial cable with a 50 Ω terminating resistor at the opposite end of the cable. This will minimize ringing by matching the cable with its characteristic impedance. If bandwidth is not important, you may increase the amount of voltage for a given light level by increasing R
## Common Operating Circuits
The DET series detectors are modeled with the circuit depicted above. The detector is reverse biased to produce a linear response to the applied input light. The amount of photocurrent generated is based upon the incident light and wavelength and can be viewed on an oscilloscope by attaching a load resistance on the output. The function of the RC filter is to filter any high-frequency noise from the input supply that may contribute to a noisy output.
One can also use a photodetector with an amplifier for the purpose of achieving high gain. The user can choose whether to operate in Photovoltaic of Photoconductive modes. There are a few benefits of choosing this active circuit:
where GBP is the amplifier gain bandwidth product and C
## Effects of Chopping Frequency
The photoconductor signal will remain constant up to the time constant response limit. Many detectors, including PbS, PbSe, HgCdTe (MCT), and InAsSb, have a typical 1/f noise spectrum (i.e., the noise decreases as chopping frequency increases), which has a profound impact on the time constant at lower frequencies.
The detector will exhibit lower responsivity at lower chopping frequencies. Frequency response and detectivity are maximized for
## Photodiode Saturation Limit and Noise Floor
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Click to Enlarge
|Spatial Uniformity Plots at Their Peak Responsivity Wavelengths|
|Click Plots for Details|
|GaP||Si||InGaAs||Ge|
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|Spatial Uniformity Plots at Various Wavelengths|
|Click Plots for Details|
|Si
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(SM1PD1A)
|405 nm||830 nm (Peak Wavelength)||1064 nm||Responsivity Plot|
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|Lot-to-Lot Consistency of SM1PD2A Photodiodes at Their Peak Responsivity Wavelength|
|Click Plots for Details|
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Measurements of dark current as a function of temperature were acquired for several unmounted photodetectors. As is described in the following section, dark current is a relatively small electrical current that flows in p-n junction photodetectors when no light is incident on the detector. Measurements were taken for silicon (Si), germanium (Ge), gallium phosphide (GaP), and indium gallium arsenide (InGaAs) reverse-biased photodiodes over temperatures from 25 °C to approximately 55 °C.
The characteristic current-voltage relationship of p-n junction photodiodes, as diagrammed in Figure 1, possesses forward-biased and reverse-biased voltage regimes. In the reverse-biased voltage regime, in which p-n junction photodiodes are operated, a potential difference applied across the diode resists the flow of current. Ideally, if no light is incident on a reverse-biased photodiode, no current flows.
Under real-world conditions, random processes in the semiconductor material of the photodiode always generates current carriers (electrons and holes) that produce current. These current generation processes are not driven by the photogeneration of electrons and holes. Instead, they are largely driven by the thermal energy contained in the semiconductor material.[1] This dark current is generally small, but it is present when the photodiode is reverse biased and not illuminated. Dark current magnitudes vary for photodiodes of different material compositions; the efficiencies of the thermal generation processes depend on the type and crystal quality of the semiconductor used in the detector's sensing head. The magnitude of the dark current can be expected to increase as the temperature of the photodiode increases.
When a photodiode is illuminated, the current generated by the incident light adds to the dark current. The carriers in the photocurrent are generated by the energy contained in the photons of the incident light. Above a certain illumination threshold intensity, the magnitude of the photocurrent exceeds the magnitude of the dark current. When the photocurrent is larger than the dark current, the magnitude of the photocurrent can be calculated by measuring the total current and then subtracting the contribution of the dark current. When the photocurrent is smaller than the dark current, the photocurrent is undetectable. Because of this, it is desirable to minimize the levels of dark current in photodiodes.
For convenience, both dark current and photocurrent are discussed as being independent of voltage over a range of voltages when the photodiode is reverse biased; however, the current flowing in real-world reverse-biased photodetectors is not completely independent of voltage over any voltage range. Regardless of whether the diode is illuminated, the current will increase as the magnitude of the reverse-bias voltage increases. In addition, if the reverse-bias voltage is increased beyond a certain threshold, the photodiode will suffer reverse breakdown, in which the magnitude of the current increases exponentially and permanent damage to the diode is likely.
Dark currents were measured over temperatures of 25 °C to approximately 55 °C for four representative unpackaged photodiodes: the Si-based
[FDS1010], the Ge-based [FDG50], the GaP-based [FGAP71], and the InGaAs-based [FGA10]. **Experimental Setup**
The experimental setup was designed to ensure a constant reverse-bias voltage across the photodiode, control the temperature of the detector, block light from reaching the detector, and establish an electrical path between the detector and the Keithley 6487 ammeter that isolated the measured current from extraneous electromagnetic interference (EMI) noise sources. Dark currents for these detectors can be on the order of nA, which made it important to control these conditions to ensure accurate measurements.
The detector enclosure consisted of a pair of nested aluminum metal boxes, which are shown with their covers off in Figure 2. Only one box would be required to create a light-tight environment for the photodiode, but an outer box was included in the setup to shield the inner box from EMI. The detector was placed inside the inner box, and it was electrically connected to the Keithley 6487 ammeter. The ammeter provided the required 5 V reverse-bias and received the output current signal. The electrical signals between the ammeter and the photodiode were routed through the two boxes using a combination of cables and feedthroughs. The 5 V bias voltage was connected to the photodiode using coax cables and BNC-to-BNC feedthroughs in the walls of both metal boxes. The current signal from the photodiode was connected to the BNC end of a BNC-to-Triax feedthrough integrated into the wall of the inner box. The signal was then routed through the outer box and to the Keithley 6487 using triax cables and a Triax-to-Triax feedthrough in the outer box. Triax cables were used because coax cables are poorly shielded, and using a coax cable to route the signal to the ammeter could introduce noise from EMI sources to the signal read from the detector. As the outer box shields the inner box from EMI, the noise introduced on the signal as it travels from the detector to the BNC-to-Triax feedthrough is mitigated.
Thermistors were used to monitor the temperatures of each photodiode continuously during the experiment. A piece of thermal tape was used to hold the thermistor flush against the TO cans of the FDG50, FGAP71, and the FGA10 during testing. The photosensor of the FDS1010 is mounted on a ceramic substrate, and when it was tested the thermistor was taped to the back of the substrate. The electrical connection between the thermistor and
[TSP01] temperature logger was performed using BNC cables, BNC-to-BNC bulkhead feedthroughs to route the signal out of the nested boxes, and a custom BNC-to-phono jack cable to connect to the temperature logger.
A custom temperature chamber based on a
[XE25C9] standard enclosure was used to conduct these tests. It is shown on top of the cart in Figure 3. The enclosure had a floor and four walls, and insulation was attached to all inner and outer surfaces. A lid for the enclosure was fashioned from a sheet of hardboard bordered with [XE25] rails, and insulation was attached to the inner surface of the hardboard. Six resistive foil heaters were affixed to the walls of the XE25C9 enclosure, and they were driven using the [PRO8000] fitted with six [TED8040] thermoelectric cooler (TEC) controller cards placed on the bottom shelf of the cart in Figure 3. Each TED8040 was interfaced with a heater and a thermistor installed in the chamber. The reading from the thermistor determined the current sent to drive the heater. The chamber was not actively cooled; cooling was instead performed by withdrawing the current driving the heaters and, as an option, opening the lid of the chamber.
The TED8040 units are designed to be interfaced with TECs, which produce heat when current flows in one direction, and which provide cooling when the current flows in the opposite direction. Because of this, when the enclosure exceeded the setpoint temperature, the TED8040 units in this experimental setup did not cut off the driving current. They instead reversed the current flow in an effort to produce cooling. In contrast to TECs, resistive foil heaters generate heat regardless of the direction of current flowing through them. In order to divert the driving current from the heaters, an electrical circuit, diagrammed in Figure 4, that included two rectifying diodes was designed and implemented. Rectifying diodes allow current to flow only in one direction. When the temperature reading from the thermistor was lower than the setpoint temperature, current flowed in the direction of the red arrows and through the resistive heater, and heat was generated. When the temperature of the enclosure exceeded the setpoint temperature, the TED8040 controllers reversed the direction of the current, so that it flowed in the direction of the blue arrows. Under this condition, the circuit diverted the current from the heaters and the chamber was allowed to cool.
**Experimental Results**
The data curves plotted in Figure 5 are the dark currents measured for the Si-based FDS1010, the Ge-based FDG50, the GaP-based FGAP71, and the InGaAs-based FGA10. Data were acquired continuously while the temperature was between 25 °C and 55 °C (shaded region of Figure 6). Figure 6 is representative of the temperature measured at the photodiode during the experiment. The temperature profile included an initial segment of increasing temperature, followed by a soak that allowed the photodiode to reach the maximum temperature, and concluded with a cool-down. The data plotted in Figure 5 include all dark current measurements measured between 25 °C and 55 °C; current measurements taken at the same temperature, but at different times, overlay one another for each diode.
The data curves plotted in Figure 5 show that the measured dark current magnitudes differed depending on the material composing the photodiode. From lowest to highest:
These span approximately 6 orders of magnitude. In all cases, the dark current increased with the temperature of the photodiode, as expected. The individual points on this graph, plotted as diamonds, are the values of the dark current specified for each detector at 25 °C. These points specify a maximum value of dark current at 25 °C; each diode's dark current must be equal to or less than this value at 25 °C, but the dark current may exceed this specification at higher temperatures, as is the case for all but the measured FDS1010 detector.
**Experimental Limitations**
Measurements were performed using a single representative of each detector type, as these data were intended to illustrate overall trends. These data should not be taken as specific for a particular diode. The measured dark current is a function of voltage bias, temperature dependence of resistive loads, and other effects. Efforts were made to suppress their influence on these measurements, including using the Keithley 6487 ammeter to provide the required 5 V reverse bias. Using the ammeter removed the need to use a load resisitor, which may exhibit its own temperature dependence. The thermistor was placed as close to the semiconductor sensor as was possible, but it was not placed in direct contact with the sensor. Because of this, there may have been a difference between the measured temperature and the temperature of the semiconductor material. The dark current was measured while the temperature of the environmental chamber was continuously varied. Humidity was not controlled during this experiment.
[1] J. Liu, Photonic Devices. Cambridge University Press, Cambridge, UK, 2005
Noise Equivalent Power (NEP) was determined as a function of temperature for several unmounted photodetectors. As is described in the following section, NEP is a common metric used to describe the minimum sensitivity of a photodetector. Measurements were taken for silicon (Si), germanium (Ge), gallium phosphide (GaP), and indium gallium arsenide (InGaAs) reverse-biased photodiodes over temperatures from 25 °C to approximately 55 °C.
The most general definition of NEP is "the input signal power that results in a signal-to-noise ratio (SNR) of 1 in a 1 Hz output bandwidth." [1] Therefore, in order to determine the NEP, the minimum noise of the photodiode must be determined. When the optical signal is blocked, noise is still present, which is generated by the detector itself. There are two main contributors to photodiode noise: the shot noise due to dark current and thermal noise due to the shunt resistance.
Dark current is a relatively small electric current present in photosensitive devices that flows through the device, including when there is no incident light. More information on the dark current can be found in the "Dark Current as a Function of Temperature" section above. Shot noise is due to the quantized nature of the charge carriers. For the case where there is no light incident on the detector, it can be calculated from the dark current of the detector using the equation [2]
where i
s is the shot noise, I d is the dark current, q is the electron charge, and f BW is the bandwidth, which will be set to 1 Hz to allow for comparison between different photodiodes.
Thermal, or Johnson, noise is due to the random thermal motion of the charge carriers. Thermal noise will be generated only by the resistive elements of the system. For the photodiode detector, the shunt resistance needs to be considered. Shunt resistance is the resistance of the zero-biased photodiode p-n junction; put another way, it is the inverse of the slope of the I-V curve at the zero-voltage point. Since it is difficult to correctly calculate the slope at the zero crossing, the generally accepted industry practice is to measure the current at V = ±10 mV and then calculate the slope. Then the thermal noise due to the shunt resistance, R
SH, can be expressed as:
where i
t is the thermal noise (expressed as a current), k B is Boltzmann's constant, T is temperature, R SH is shunt resistance, and f BW is the bandwidth.
The total noise, i
total, is the quadrature sum of all noise sources:
Note that this result is the total noise expressed for the current output of the photodiode, while the NEP is expressed in terms of incident optical power. Thus, to compare with the NEP specifications a typical responsivity value,
, is chosen for the specified wavelength:
Also, to allow for comparison between different diodes, we set the bandwidth to 1 Hz for the calculation.
NEP was determined over 25 to 55 °C for four representative unpackaged photodiodes: the Si-based
[FDS1010], the Ge-based [FDG50], the GaP-based [FGAP71], and the InGaAs-based [FGA10]. **Experimental Setup**The experimental setup was designed to ensure a constant reverse-bias voltage across the photodiode, control the temperature of the detector, block light from reaching the detector, and establish an electrical path between the detector and the Keithley 6487 ammeter that isolated the measured current from extraneous electromagnetic interference (EMI) noise sources. Dark currents for these detectors can be on the order of nA, which made it important to control these conditions to ensure accurate measurements.
The detector enclosure consisted of a pair of nested aluminum metal boxes, which are shown with their covers off in Figure 1. Only one box would be required to create a light-tight environment for the photodiode, but an outer box was included in the setup to shield the inner box from EMI. The detector was placed inside the inner box, and it was electrically connected to the Keithley 6487 ammeter. The ammeter provided the required reverse-bias voltage and received the output current signal. The electrical signals between the ammeter and the photodiode were routed through the two boxes using a combination of cables and feedthroughs. The bias voltage was connected to the photodiode using coax cables and BNC-to-BNC feedthroughs in the walls of both metal boxes. The current signal from the photodiode was connected to the BNC end of a BNC-to-Triax feedthrough integrated into the wall of the inner box. The signal was then routed through the outer box and to the Keithley 6487 using triax cables and a Triax-to-Triax feedthrough in the outer box. Triax cables were used because coax cables are poorly shielded, and using a coax cable to route the signal to the ammeter could introduce noise from EMI sources to the signal read from the detector. As the outer box shields the inner box from EMI, the noise introduced on the signal as it travels from the detector to the BNC-to-Triax feedthrough is mitigated.
For dark current measurements, the bias voltage was set to 5 V. In order to calculate the shunt resistance, measurements of the current were made with the bias voltage set to +10 mV and -10 mV.
Thermistors were used to monitor the temperatures of each photodiode continuously during the experiment. A piece of thermal tape was used to hold the thermistor flush against the TO cans of the FDG50, FGAP71, and the FGA10 during testing. The photosensor of the FDS1010 is mounted on a ceramic substrate, and when it was tested the thermistor was taped to the back of the substrate. The electrical connection between the thermistor and
[TSP01] temperature logger was performed using BNC cables, BNC-to-BNC bulkhead feedthroughs to route the signal out of the nested boxes, and a custom BNC-to-phono jack cable to connect to the temperature logger.
A custom temperature chamber based on a
[XE25C9] standard enclosure was used to conduct these tests. It is shown on top of the cart in Figure 3. The enclosure had a floor and four walls, and insulation was attached to all inner and outer surfaces. A lid for the enclosure was fashioned from a sheet of hardboard bordered with XE25 rails, and insulation was attached to the inner surface of the hardboard. Six resistive foil heaters were affixed to the walls of the XE25C9 enclosure, and they were driven using the PRO8000 chassis fitted with six [TED8040] thermoelectric cooler (TEC) controller cards placed on the bottom shelf of the cart in Figure 2. Each TED8040 was interfaced with a heater and a thermistor installed in the chamber. The reading from the thermistor determined the current sent to drive the heater. The chamber was not actively cooled; cooling was instead performed by withdrawing the current driving the heaters and, as an option, opening the lid of the chamber.
The TED8040 units are designed to be interfaced with TECs, which produce heat when current flows in one direction, and which provide cooling when the current flows in the opposite direction. Because of this, when the enclosure exceeded the setpoint temperature, the TED8040 units in this experimental setup did not cut off the driving current. They instead reversed the current flow in an effort to produce cooling. In contrast to TECs, resistive foil heaters generate heat regardless of the direction of current flowing through them. In order to divert the driving current from the heaters, an electrical circuit, diagrammed in Figure 3, that included two rectifying diodes was designed and implemented. Rectifying diodes allow current to flow only in one direction. When the temperature reading from the thermistor was lower than the setpoint temperature, current flowed in the direction of the red arrows and through the resistive heater, and heat was generated. When the temperature of the enclosure exceeded the setpoint temperature, the TED8040 controllers reversed the direction of the current, so that it flowed in the direction of the blue arrows. Under this condition, the circuit diverted the current from the heaters and the chamber was allowed to cool.
**Experimental Results**
The data curves plotted in Figure 4 are the dark currents measured for the Si-based FDS1010, the Ge-based FDG50, the GaP-based FGAP71, and the InGaAs-based FGA10. Figure 5 shows the calculated shunt resistance values for the same diodes as Figure 4. Data were acquired continuously while the temperature was between 25 °C and 55 °C (shaded region of Figure 7). Figure 7 is representative of the temperature measured at the photodiode during the experiment. The temperature profile included an initial segment of increasing temperature, followed by a soak that allowed the photodiode to reach the maximum temperature, and concluded with a cool-down. The data plotted in Figures 4 and 5 include all dark current measurements measured between approximately 25 °C and 55 °C; current measurements taken at the same temperature, but at different times, overlay one another for each diode.
As shown in Figure 5, the shunt resistance for the measured GaP, InGaAs, and Si detectors is relatively large; therefore in many situations it can be ignored. For the Ge-based FDG50 the shunt resistance is relatively low, especially at higher temperatures. For this diode the shunt resistance might need to be considered if there is a high load involved.
Figure 6 shows the calculated NEP vs. temperature for each diode. Since the NEP is a function of responsivity, which varies with wavelength, the NEP values are calculated at the peak responsivity value as given in the table to the right.
|Responsivity Used for NEP Calculation|
|FGA10||1.05 A/W @ 1550 nm|
|FDG50||0.85 A/W @ 1550 nm|
|FGAP71||0.12 A/W @ 440 nm|
|FDS1010||0.725 A/W @ 970 nm|
The data curves plotted in Figure 6 show that the calculated NEP magnitudes differed depending on the material composing the photodiode. From lowest to highest:
These span approximately 6 orders of magnitude. In all cases, the dark current increased with the temperature of the photodiode, as expected. The individual points on this graph, plotted as diamonds, are the values of the dark current specified for each detector at 25 °C. These points specify a maximum value of dark current at 25 °C; each diode's dark current and NEP must be equal to or less than this value at 25 °C, but the dark current and NEP may exceed this specification at higher temperatures.
**Experimental Limitations**
Measurements were performed using a single representative of each detector type, as these data were intended to illustrate overall trends. These data should not be taken as specific for a particular diode. The measured currents were functions of voltage bias, temperature dependence of resistive loads, and other effects. Efforts were made to suppress their influence on these measurements, including using the Keithley 6487 ammeter to provide the required 5 V reverse bias. Using the ammeter removed the need to use a load resistor, which may exhibit its own temperature dependence. The thermistor was placed as close to the semiconductor sensor as was possible, but it was not placed in direct contact with the sensor. Because of this, there may have been a difference between the measured temperature and the temperature of the semiconductor material. The currents were measured while the temperature of the environmental chamber was continuously varied. Humidity was not controlled during this experiment.
[1] Thorlabs'
[Noise Equivalent Power White Paper](images/TabImages/Noise_Equivalent_Power_White_Paper.pdf).
[2] Quimby, Richard S. Photonics and Lasers: An Introduction. Wiley-Interscience, Hoboken, NJ, 2006, pp 241-244.
We present laboratory measurements showing the effect of beam size on the saturation point of a Thorlabs silicon photodiode. As defined here, saturation is a 1% deviation from the linear response region. As illustrated in Figure 1, the photodiode saturated at lower incident power levels as the beam size decreased. Several additional calculations and experiments were performed to verify the cause of the change in saturation was not a function of the power density. These results suggest that users should be cognizant of the beam size when attempting to measure absolute power with a power sensor, such as our
[S130C] photodiode power sensor.
For our experiment, we used the
[SM1PD1A] mounted photodiode, which consists of an [FDS1010] photodiode in an SM1-threaded housing. An 830 nm superluminescent diode was used as the light source. A beamsplitter directed 20% of the light to a monitor photodiode while the remainder was transmitted through a focusing lens. Power values were calibrated using an integrating sphere, while the beam size of the focusing beam was calibrated with a beam profiler mounted to a translation stage. After calibration, the beam profiler was replaced with the device under test (DUT), an SM1PD1A at a 0 V bias. The output current was measured with an ammeter to remove the need for a load resistor. We then recorded datasets as the beam diameter was continuously scanned from 0.06 mm to 5 mm while power was held constant, as well as measurements for beam diameters ranging from 1 mm to 5 mm (measured to the 5% clip level) as the incident power was continuously scanned from 0.12 mW to 5 mW.
The figures show the results from the measurements. Figure 1 (right) and Figure 2 (below) show the deviation from linear response for continuously varying beam diameter at a fixed 1 mW incident power (Figure 1) and continuously varying incident power for several beam diameters (Figure 2). Figure 1 shows that for a 1 mW input, the photodiode saturated at beam sizes less than 300 µm. Figure 2 shows that beam diameters ≥2 mm did not saturate at the power levels investigated.
One hypothesis for these results was that local saturation due to a large power density locally depleted or reduced the population of available carriers. In Figure 3, we calculated the power density by taking the quotient of the measured power and beam diameter presented in Figure 2 and plotted the current output as a function of that power density. If the results were due to local saturation, we would have expected that all of the beam diameters would saturate at a single power density; however, this was not the case.
Since the results presented in Figure 3 coupled the beam size change with a change in optical power density, we performed another experiment to increase the power density incident on the sensor within the same envelope of beam area to see if there was a change in the saturation point. This was done by segmenting the Gaussian beam into an array of beamlets with a microlens array, concentrating the overall optical power into smaller spots within the same Gaussian envelope. This created larger power densities while maintaining a similar electrical path to the sensor leads. Figure 4 shows the same results as Figure 2 with the results from the microlens array overlaid as dashed lines. Since the results are nearly identical to the original Gaussian beam for all diameters, the saturation appears to be dependent on the overall beam diameter and independent of the power density. In the
[complete Lab Facts presentation](images/TabImages/Beam_Size_and_photodiode_Saturation_LabFact.pdf), we discuss how these results support the theory of Scholze *et al.* that the change in saturation with beam size is due to a change in the series resistance of the photodiode [1].
[1] F. Scholze, R. Klein, R. Muller, Linearity of silicon photodiodes for EUV radiation. 2004 Proc. SPIE 5374 926–34.
**About Our Lab Facts**
Our application engineers live the experience of our customers by conducting experiments in
[Alex’s](about_us.cfm) personal lab. Here, they gain a greater understanding of our products’ performance across a range of application spaces. Their results can be found throughout our website on associated product pages in *Lab Facts* tabs. Experiments are used to compare performance with theory and look at the benefits and drawbacks of using similar products in unique setups, in an attempt to understand the intricacies and practical limitations of our products. In all cases, the theory, procedure, and results are provided to assist with your buying decisions.
|Posted Comments:|
Poster:
marty.lawson
Posted Date:
2017-02-01 12:49:31.84
How large of a fiber optic core can the the FDS02 photo-diode be used with before coupling efficiency drops?
Poster:
tfrisch
Posted Date:
2017-02-16 02:14:08.0
Hello, thank you for contacting Thorlabs. While the active area is 250um in diameter, the largest fiber we have that is smaller than that would be a 200um core. The FDS02 does not include a ball lens between the fiber and the detector. I will reach out to you with more details.
Poster:
faryads
Posted Date:
2016-03-22 21:36:37.053
Hi, is the FGA01FC a multi-quantum-well structure photodiode?
Poster:
besembeson
Posted Date:
2016-03-25 12:26:10.0
Response from Bweh at Thorlabs USA: The FGA01FC is not a multi-quantum-well structure. This is simply a doped InGaAs material to create a P-N junction for charge transfer when illuminated by light of suitable wavelength. Quantum wells on the other hand are heterostructure made by joining materials, in layers at the atomic level, which typically leads to an emission.
Poster:
akpabioubongabasi
Posted Date:
2016-02-29 14:16:38.723
Please I need a Photodector with wide sensing area, a wavelength of 650nm and which comes with an SMA Connector
Poster:
besembeson
Posted Date:
2016-03-09 12:16:53.0
Response from Bweh at Thorlabs USA: The SM05PD1A (Large Area Mounted Silicon Photodiode, 350-1100 nm, Cathode Grounded) could be a suitable recommendation. Others can be found at the following link on our website: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1285
Poster:
Posted Date:
2015-10-16 14:16:32.147
What is the series and shunt resistance of FDS100?
Poster:
besembeson
Posted Date:
2015-10-27 04:54:33.0
Response from Bweh at Thorlabs USA: We don't have the exact values from the manufacturer of the photodiode but the shunt resistance should be in the Giga Ohm range while the series resistance should be extremely low that it can be negligible.
Poster:
ehrler
Posted Date:
2015-09-24 03:41:03.583
Do you offer calibration for the DSD2 photodiode? Thanks!
Poster:
besembeson
Posted Date:
2015-10-08 12:06:35.0
Response from Bweh at Thorlabs USA: This is not possible for the DSD2. There is a limitation to the minimum detector size for us to do such calibration, which is 2mm minimum. The InGaAs sensor is only about 1.5mm.
Poster:
jarkko.piirto
Posted Date:
2015-03-24 10:27:03.187
I would need a photodiode set up with specific mount (3pcs) for picosecond laser alignment. Focused spot size (1/e2) is <100µm. Succesfull guidance will mean purchase..
Poster:
jlow
Posted Date:
2015-03-24 04:42:43.0
Response from Jeremy at Thorlabs: We will need more information on your application first. We will contact you directly about this.
Poster:
aklossek
Posted Date:
2014-05-09 07:48:19.477
Dear ladies and gentlemen, I am looking for a Si photodiode for a stimulated raman microscope, where the modulation of a ps-laser beam must be detected. The diode has to work in MHz range, quite large active area and must be sensitive between 800 and 1000nm. Up to now I thought about the DET100A. But now I have doubts that it will saturate to fast. Can you suggest another diode, which saturates at high powers to detect the laser beam. Best regards André Klossek
Poster:
jlow
Posted Date:
2014-05-13 08:43:47.0
Response from Jeremy at Thorlabs: I will contact you directly to get more information on your application and make a recommendation.
Poster:
tanzwei
Posted Date:
2013-05-05 06:39:49.27
Could you like to tell me the damage threshold of FGA10 ?
Poster:
jlow
Posted Date:
2013-05-09 11:19:00.0
Response from Jeremy at Thorlabs: I would recommend keeping the output current to be <10mA to avoid the internal wire in the FGA10 from failing. You can estimate the output current for your input power and wavelength from the responsivity graph on the 2nd page of the spec sheet at http://www.thorlabs.com/Thorcat/2200/FGA10-SpecSheet.pdf.
Poster:
jlow
Posted Date:
2012-10-24 16:14:00.0
Response from Jeremy at Thorlabs: There's a ball lens covering the chip and it is not AR coated.
Poster:
t.schmoll
Posted Date:
2012-10-18 13:30:14.92
Is there a window or a ball lens covering the chip? Is the window or ball lens AR coated? If so, for which wavelength is it optimized? Thank you! Tilman
Poster:
jlow
Posted Date:
2012-09-05 09:15:00.0
Response from Jeremy at Thorlabs: I will get in contact with you directly to discuss about your application.
Poster:
kkkdane
Posted Date:
2012-09-03 10:17:41.0
Hi, I’m a researcher in South of Korea Recently, I am developed infrared moisture detector. And I used LED and PD that is your product. I have a question. What is the question PD, LD(laser diode) and LED that use infrared moisture detector or infrared moisture analyzer? Recently, What other companies use the LED, PD that used the water detector of Commercial products? And what is commercial product? And, If you will give a detailed information about the LED, PD. I appreciate your help.
Poster:
jlow
Posted Date:
2012-08-23 16:31:00.0
Response from Jeremy at Thorlabs: The junction capacitance between 4V and 5V is pretty much flat. Unfortunately we do not have any data on the capacitance and fall time specs beyond 5V.
Poster:
Mathias.Helsen
Posted Date:
2012-08-22 06:14:07.0
I would like to use this diode as a detector for microwave modulated light, but the fall time at 5V is too high. How much doe the capacitance and fall time change when the bias voltage is increased?
Poster:
jlow
Posted Date:
2012-08-17 11:16:00.0
Response from Jeremy at Thorlabs: We are not able to disclose the thicknesses for the PIN layers.
Poster:
cardoza.david
Posted Date:
2012-08-17 09:50:00.0
Is there a way to get find out the thickness of the p, i and n regions of the FDS010 diodes? Thank you.
Poster:
jlow
Posted Date:
2012-08-16 13:42:00.0
Response from Jeremy at Thorlabs: I will get in contact with you directly for the Excel spreadsheet. Please note that the spectral responsivity of your photodiode can be quite different than what is shown online. One alternative to using the FDS100 is the FDS100-CAL (http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=2822&pn=FDS100-CAL) which is the NIST calibrated version of the FDS100.
Poster:
brian.cox
Posted Date:
2012-08-16 12:13:51.0
Is the raw spectral responsivity data for the FDS100 available in an Excel spreadsheet? I'd like to get a more exact A/W value for my specific wavelengths of interest. Thanks!
Poster:
tcohen
Posted Date:
2012-03-22 14:27:00.0
Response from Tim at Thorlabs: Thank you for your feedback. If the window is removed the diode can be easily damaged and absorb water from the atmosphere. This will be detrimental to the performance of the FGA10. If the window is removed we recommend storing it in an N2 dry box.
Poster:
frank
Posted Date:
2012-03-22 13:31:41.0
Can you tell me if the performance of the FGA10 will degrade if its window is removed?
Poster:
bdada
Posted Date:
2012-03-16 12:33:00.0
Response from Buki at Thorlabs: Thank you for your suggestion. We will work on adding dark current vs bias voltage charts to our website.
Poster:
Posted Date:
2012-03-15 19:02:40.0
Please consider adding a plot that shows the dark current as a function of bias voltage.
Poster:
bdada
Posted Date:
2012-01-31 23:43:00.0
Response from Buki at Thorlabs: The temperature does have a slight effect on the responsivity, but mostly in near the bandgap region. We have sent you some typical curves to review.
Poster:
ale.cere
Posted Date:
2012-01-30 12:27:49.0
I am currently working with a FDG05 and I notice that the efficiency changes with temperature, as indicated also in the datasheet. Is it available any data regarding the expected change in responsivity as funcion of temperature?
Poster:
jjurado
Posted Date:
2011-07-07 09:57:00.0
Response from Javier at Thorlabs to jasiel.mora: Thank you very much for contacting us! We actually show a recommended circuit diagram for our photodiodes on their spec sheets. Take a look at the spec sheet for the FDG03 here: http://www.thorlabs.com/Thorcat/13800/13846-S01.pdf I will contact you directly in case you have any further questions.
Poster:
jasiel.mora
Posted Date:
2011-07-06 16:42:48.0
Could you please sugest any connection diagram for the sensor FDG03? Thanks.
Poster:
jjurado
Posted Date:
2011-04-20 12:09:00.0
Response from Javier at Thorlabs to last poster: Thank you very much for contacting us. The shunt resistance of the FDS1010 photodiode is in the range of 50-200 MOhm (@ 10 mV reverse bias). Also, we have added a graph of the maximum, average, and minimum responsivity values for the FDS1010 (See Responsivity Graphs tab). Please contact us at techsupport@thorlabs.com if you have any further questions or comments.
Poster:
Posted Date:
2011-04-20 13:08:43.0
What is the shunt resistance of FDS1010? Its not in the specs. A typ. and min. responsivity value would be useful as well.
Poster:
julien
Posted Date:
2011-01-18 16:08:51.0
A response from Julien at Thorlabs: The FGA04 can only be calibrated at a predefined fixed wavelength by using a fiber coupled laser source. A calibration over the whole wavelength range of this photodiode is unfortunately not possible due to its small active area. Such a calibration would be made in free space using a monochromator, whose output beam diameter is about 1.5mm. Such a beam would largely overfill the active sensor area, and thus make the calibration highly inaccurate. You can contact our tech support (techsupport@thorlabs.com) to further discuss which solutions could be adapted to your need
Poster:
Posted Date:
2011-01-18 17:46:35.0
why a NIST-traceable calibration is not possible for FGA04? Im looking for a fiber-coupled detector that is provided with calibration.
Poster:
kleap
Posted Date:
2010-10-28 13:45:47.0
Our FDG05 are failing roughly 3 months of use. What is the expected life of these detectors? We are exposing indirect UV light around 5W/cm2 of intensity to the LADs. Could this be of a concern?
Poster:
Thorlabs
Posted Date:
2010-10-28 15:01:31.0
Response from Javier at Thorlabs to kleap: at 5 W/cm^2, the detector will most likely be saturated; however, we specify a damage threshold of 10 W/cm^2 for the FDG05, so I do not expect excessive power to be the reason for failure. Also, we do not have a lifetime spec, since there are too many factors involved. I will contact you directly to troubleshoot your application.
Poster:
Thorlabs
Posted Date:
2010-07-23 14:06:31.0
Response from Javier at Thorlabs to ranutyagi: Thank you for your feedback. With an input of 10 mW, you will most likely end up damaging your photodiodes. As a guideline, we specify a maximum input power density of 100 mW/cm^2. So, for example, if we assume that you have a 10 mW, 2 mm diameter beam at the input, the resulting power density is ~333mW/cm^2, which clearly exceeds the damage threshold. For linear operation of the photodiode, we recommend limiting the input to ~ 1 mW. Above this value, the diode undergoes saturation and, eventually, damage.
Poster:
ranutyagi
Posted Date:
2010-07-23 07:03:58.0
I am using FDS100 and FDS010 with CW 10mW peak power laser diode. will it be damaging my photodiode? How much is the maximum input power these diodes can sustain.
Poster:
Adam
Posted Date:
2010-04-29 16:58:35.0
A response from Adam at Thorlabs to marcoc: Saturation occurs for these diodes at approximately 10mW. We would suggest using these diodes with peak and average powers that are less than 10mW if you want to avoid saturation.
Poster:
marcoc
Posted Date:
2010-04-29 16:51:34.0
Any idea about the saturation for pulsed (50fs) laser beam at 800 nm ? thanks marco
Poster:
apalmentieri
Posted Date:
2010-01-14 15:34:33.0
A response from Adam at Thorlabs to Curtis: The operating and storage temperature ranges for the FDS100 are the following: -25 to +85 deg C operating, -40 to +100 deg C storage.
Poster:
curtis.m.ihlefeld
Posted Date:
2010-01-14 15:12:09.0
Dear Sirs, I have several FDS100 photodiodes and would like to know the allowable temperature ranges for operation and storage. Regards, Curtis Ihlefeld
Poster:
danhickstein
Posted Date:
2009-08-07 14:16:56.0
Dear Thorlabs, It would be nice to have the wavelength response for the FDS02 plotted on the Graphs page. I found the graph on the spec sheet, but it would be nice to see it plotted on the same graph as the rest of the FDS series. Regards, Dan
Poster:
Tyler
Posted Date:
2009-02-02 09:25:34.0
A response from Tyler at Thorlabs to ocarlsson: The FGA04 spec sheet available under the Drawings and Documents tab lists the max forward current as 10 mA and the damage threshold at 70 mW. The damage threshold is the point at which the photodiode sensor will fail, however, internal wires in the FGA04 package will fail when the forward current exceeds 10 mA. Use the responsivity curve in the spec sheet to approximate the forward current for a given wavelength or contact our technical support department for assistance. An optical fiber attenuator like the FA05T, FA10T, FA15T, or FA25T can be used in to reduce the power in the optical fiber to a level that is safe to use with the FGA04. Thank you for your question, I will be adding a note to the bottom of the table on the Specs tab to help future customers with this issue.
Poster:
ocarlsson
Posted Date:
2009-01-16 02:31:20.0
The FGA04 max current is 10mA and damage threshold is 100mW. Responsivity 0.8. How is the damage threshold calculated? Best regards Olle
The following table lists Thorlabs' selection of photodiodes and photoconductive detectors. Item numbers in the same row contain the same detector element.
|Photodetector Cross Reference|
|Wavelength||Material||
|
|
|Click Image
for Details
|
|![]()
|
|Click Image
for Details
|
|![]()
|Item #||Info||Wavelength
|
Range
|Active
|
Area
|Package||Rise/Fall
|
Time
a |NEP
|
(W/Hz
1/2) |Dark
|
Current
|Junction
|
Capacitance
|Compatible
|
Sockets
|
|DSD2 |
|![]()
|
|Click Image
for Details
|
|![]()
2017-07-17 15:09:46.207 tfrisch 2017-08-09 05:35:48.0

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# Adsense Optimization
Ngân sách $250-750 USD
Music blog with 7k-11k daily traffic needs an
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Require Google Adsense Expert - Increase CTR / Revenue
## Đã trao cho:
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Thank you for inviting me to bid on your Adsense Optimization project. See PMB for more information!!
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# 130284 Longterm blogwriter on finance
Ngân sách N/A
I would require a good long term writer to write blogs 3 times a week,every mon/wed/fri few articles with keyword rich content pertaining to investment/wealth creation/wealth management/savings/insurance/forex/options/
Need not be well verse in these areas,as long
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2) able to get wide variety of knowledge/tips from other sources/internet, from basics to advance also can.
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Project is long term hence cost bids are taken as factor. Have few other projects in mind in later half of year so if good would like to retain writer. Blog and website is [url removed, login to view] and [url removed, login to view]
I could give financial news/materials pertaing to local newspapers (including my username and password I paid for) + articles from various financial/investment sites. Best if could also get info or materials from other sources
Please bid for project.
Factors to consider:
1) Cost
2) Long term


markdown:
# Online Data Entry - Online Filling Form
Ngân sách $750-1500 USD
We are Data Entry Company,with based in US, New York.
We need freelancers only from US for online data entry jobs.
For simple typing jobs, online filing forms, copy-paste.
You must have internet connection, and basic typing skills.
Our Company pay you 5-10$ per complete form.
Thanks for the interest.
## 17 freelancer đang chào giá trung bình $868 cho công việc này
[JeffDavis954](/u/JeffDavis954)
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I will fly through your forms & your company will be very pleased.
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markdown:
# Article Writing - Technical / Software Related
Ngân sách $30-250 USD
Looking for original (must be original) articles about a particular type of software product and the features products of this type have. Will require a little research about a feature/functionality, then write an article of 400-500 words.
All articles will be written about the same software product/niche, so there will not be ongoing research.
Please provide examples of tech articles you have written - preferably links to your online work.
Articles become my property after you receive payment and may not be re-used.
Please submit a bid based on 10 articles.
PM any questions. Thank you.
## Đã trao cho:
## 19 freelancer đang chào giá trung bình $67 cho công việc này
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markdown:
Đã Hủy
# Complete web site re-write
Ngân sách $100-300 USD
I need a complete re-write of a current web site that has financial information.
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The re-write should be done with SEO in mind, by someone very familiar with the new changes from the Google's algo...
If you are not aware about those changes(as reported in some very well known SEO forums) please do not bid!


markdown:
# Pervasive (btrieve) data extraction
Ngân sách $30-250 USD
I have a number of files with the extension .dat files that need to be extracted into Access. I will parse and check the data to ensure accuracy. Payment will be reduced for inaccuracy or incompleteness. I will pay through escrow to ensure fairness on both sides. Bidding ends April 30th.
## 9 freelancer đang chào giá trung bình $93 cho công việc này
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markdown:
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# Flash XML Analogue Meter
Ngân sách $30-60 USD
Hi i need a very basic thing
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when page loads the needle will rotate animate from 0 to value
my budget is


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