In numerous electronic communication applications, optical assemblies are used in various optical circuits. A typical optical assembly may comprise an optical source, an optical circuit that modulate, filter, mix optical and electronic signals and an optical fiber that connect the assembly to other element in an optical system. By combining various element in an optical assembly it is possible to create various optical elements. For example an optical assembly for a telecommunication system may comprises several semiconductor lasers, optical modulators and multiplexers to generate WDM signals that can be sent over an optical fiber. A second example for an optical assembly might be an assembly for detection of wavelength of a fiber Bragg grating in an optical sensing systems. The assembly may include one or several semiconductor optical sources, electro-optic modulators, wavelength de-multiplexers and wavelength detecting elements and optical detectors. The assembly is generally integrated and packaged into small form factor electronic packages and optical fibers and wires connect the assembly to external elements in the system.
Several methods have been used in the past to achieve integrated optical assemblies.
In one example, US2011/0013869A1 publication discloses a method for creating an optical assembly by using a plurality of small micro-lenses that are manipulated by a micro-electromechanical devices in order to achieve necessary alignment tolerances. This method for making an optical assembly requires a plurality of small optical lenses and individual alignment for each lens.
Furthermore, for coupling light from an optical fiber to a high-index contrast waveguide, several methods have been disclosed in the past. In one example, US2010/0135615A1 and U.S. Pat. No. 7,643,719B1 publications disclose a coupling mechanism based on a graded-index (GRIN) lens, which is deposited on a substrate's surface and is etched into the substrate to form a GRIN lens in the vertical direction. In this example, a patterned edge is created and forms a curved surface for horizontal focusing in order to couple light from an optical fiber to a high-index contrast waveguide. The GRIN lens method disclosed in these publications requires a precise control of refractive index profile, and it is generally difficult to manufacture an exact refractive index profile with a high level of precision.
Other conventional methods for coupling light from an optical fiber to high-index contrast waveguides include using grating couplers. For example, U.S. Pat. No. 5,033,812 and U.S. Pat. No. 5,101,459 publications disclose a grating device formed on the surface of the device. In this example, the grating device is used to couple the light from an optical fiber or free space to the high-contrast waveguide.
Another type of conventional coupling method is related to tapered waveguides for coupling of optical energy between an optical fiber and a high-index contrast waveguide. For example, U.S. Pat. No. 7,239,779B2 discloses a method to achieve optical coupling via transfer of energy between waveguides on different layers. This method related to tapered waveguides were used for coupling optical energy between an optical fiber and a high-index contrast waveguide.
A micro-mirror for board-level interconnects is disclosed in the publication “F. Wang et. al, Optics Express, Vol 17, No 13, pp 10514, 2009”. In this method of fabrication a 45 degree reflection surface is created in a polymer film by exposure at an angle inside water to make a 45 degree reflecting surface.
It may also be beneficial to devise a novel method to couple light from a semiconductor laser to high-index contrast waveguide in an optical assembly and also couple light between single mode optical fiber to a high-index contrast optical waveguide. Because the mode size of a nano-waveguide is very small compared to the mode size of an optical fiber (i.e. typically less than 1 micron for a nano waveguide, compared to 10 microns for an optical fiber), the coupling efficiency from an optical fiber to a high-index contrast waveguide is very poor. Furthermore, due to a large diffraction of light, the coupling efficiency between semiconductor lasers and planar optical waveguides is often unsatisfactory.
Therefore, a novel optical assembly apparatus that can couple light with improved coupling efficiency between a semiconductor laser and a planer high-index contrast waveguide, or between an optical fiber and a planer high-index contrast, may be desirable. Furthermore, a novel method to manufacture and process such novel optical assembly apparatuses may also be desirable. In addition, a novel method to tune a wavelength of the laser by utilizing the novel optical assembly apparatus may also be desirable.