Repeat problem 16.1 for a bias current of 150 mA, all other conditions remaining the same.
A cw double heterojunction GaAs-GaAlAs laser diode is to be directly current modulated by a sinusoidal ac signal current of 100 mA peak-to-peak.
What must be the minimum dc bias current to the laser to ensure that the laser
output linearly follows the input signal, i.e., the output optical signal will be
sinusoidal, following the input signal current waveform. Relevant characteristics of the laser diode are as follows:
(1) Emitted wavelength: 9000 A. ˚
(2) 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. ˚
(3) Index of refraction: 3.3.
(4) Thickness of active layer 1 μm.
(5) Internal quantum efficiency: 0.8.
(6) Average absorption coefficient: 10 cm−1.
(7) Length between cleaved end faces: 1 mm.
(8) Reflectivity of end faces: 0.4.
(9) Cross-sectional area normal to current flow: 10−3 cm2.