We would like to design a p-n junction laser for use as the transmitter in a
range finder. The output is to be pulsed with a peak power out of each end
of 10 W (only the output from one end will be used) and a pulse duration of
100 ns. Wavelength is to be 9000 A. Room temperature operation is desired ˚
and some of the pertinent parameters have been either measured or established so that:
(1) Half-power points of the emission peak for spontaneous emission have
been measured for this material at room temperature to be at 9200 and
8800 A. ˚
(2) Index of refraction: 3.3.
(3) Thickness of light invertemitting layer: 10 μm.
(4) Thickness of active (inverted pop.) layer: 1 μm.
(5) Internal quantum efficiency: 0.7.
(6) Average absorption coefficient: 30 cm−1.
(7) W = 300 μm.
(8) Reflectivity of the Fabry-Perot surfaces: 0.4.
(a) What must be the separation between Fabry-Perot surfaces if we
wish to have a peak pulse current density of 3 × 104 A/cm2?
(b) What is the threshold current density?