to direct photons to detection region 332 alternatively one or more light source can be positioned above circuit 300 or at an oblique angle to circuit 300 so as to direct photons to detection region 332 this results is reduced internal scattering and attenuation of the incident exciting photons the multitude of photons reaching detection region 332 can be absorbed by the sample scatter upon reaching the sample or be emitted by the substance present at this region the scattered or emitted photons are schematically shown by arrows 358 in one embodiment the photons source is selected from the group consisting of a laser and a light emitting diode in another embodiment the photon source can have a wavelength in one of the infrared the near infrared the visible ultraviolet or x ray wavelength range in still another embodiment the photon sources is selected from the group consisting of electro generated luminescence and chemi luminescence in still another embodiment a plurality of photon sources are provided where each source provides photons in one or more of the above cited exemplary wavelength ranges in still another embodiment a brad band photons sources is passed through a narrow pass filter and then used as an illumination source thus an exemplary spectrum can be one of a raman luminescence e g fluorescence near infrared an infrared ultraviolet or an x ray spectrum in one embodiment the wavelength of the source is in the range of about 15 25 cm u2212 1 lens 360 is positioned above a region of the microfluidic circuit to receive optical emitted or.