In most practical applications of interest is the power received by detector rather than the integral power of the LED. That’s why practical constructions contain beam concentrators and lenses. The above described episide-down bonded LEDs well suite for the coupling with the optical details since their emitting surface is flat and is free of any contacts. That’s why it was not difficult to couple them with the Si or CdSb immersion lens (D=3 mm, H=3 mm) by gluing them onto n⁺-InAs through the chalcogenide glass having refractive index n=2.6 and melting temperature of about 60^oC.

One of the advantages of the LEDs is the concentration of the output beam shown in the right picture. The narrowing of the far field beam pattern in the lens coupled LED is beneficial for the coupling with detectors e.g. having the same lenses and construction. The output of the developed LEDs is at least three times higher than that of the published analogs that creates good perspective for their practical applications in various gas analyzers.

1-Si or CdSb immersion lens D=3.5 mm, 2- epoxy, 3-chalcogenide “glue”, 4 –“flip chip bonded” LED or BSI photodiode, 5-Si submount, 6-TO-39 header, 7-cathode, 8-anode