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InGaAs quantum wells and a Bragg mirror structure are grown on a GaAs substrate to simultaneously serve as a low-loss saturable absorber and an output coupler for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 946 nm. With an incident pump power of 9.2 W, the laser produces pulses of 38 ns duration with average pulse energy of as much as 20 [micro]J at a pulse repetition rate of 55 kHz. OCIS codes: 140.3480, 140.3540, 140.3580.

A diode-pumped Yb:YCOB laser at 1086 nm is passively Q switched by using InGaAs quantum wells as saturable absorbers and utilizing the Bragg mirror structure as an output coupler. With an absorbed pump power of 9.2 W the laser produces pulses of 100 ms duration with average pulse energy of as much as 165 [micro]J at a pulse repetition rate of 7 kHz. OCIS codes: 140.0140, 140.3540, 140.3580.

A low-loss semiconductor saturable absorber based on InGaAs quantum wells was developed for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 1123 nm. With an incident pump power of 16 W, an average output power of 3.1 W with a Q-switched pulse width of 77 ns at a pulse repetition rate of 100 kHz was obtained. OCIS codes: 140.3480, 140.3540, 140.3580.

Research was conducted to examine the influence of modulating field on the photoreflectance of surface-intrinsic-n+ (s-i-n+) type doped GaAs simulated by electroreflectance. Several Franz-Keldysh oscillations were observed from the simulated spectra of the s-i-n+ sample which allowed the determination of the electric field. The relationship between the calculated electric field strength (F) and delta-F was investigated for the whole range of delta-F.

A study was conducted to show that the emission wavelength of (InP)2/(GaP)2 short-period superlattice quantum wells can be changed by altering the tilt angle of the substrate or by adjusting the interruption time during switching. Variable temperature photoluminescence spectroscopy was carried out to characterize the samples. Results indicated that the growth mechanism can be determined through the bonding preference between the group III adatoms on the surface.

Researchers measured the electroreflectance (ER) spectra of undoped-n+ type doped GaAs at different modulating field magnitudes (deltaF). They found many Franz-Keldysh oscillations (FKOs) and, by applying fast Fourier transformation to the FKOs, they were able to determine the electric field. The power spectrum resolves into two peaks when deltaF is small in comparison to the built-in field, and, under these conditions, F is almost uncorrelated with deltaF. However, F increases with deltaF at correspondingly larger deltaF.

Instability due to an external cavity effect in the output of dc-biased surface emitting lasers was investigated. The results showed that the output power spectrum had multiple peaks with spacing corresponding to the round-trip delay in silica fibers. Peak magnitude was enhanced in the spectral region centered at the laser relaxation frequency. Increased feedback resulted in a corresponding increase in the output spectrum.

The effect of thin protective InAs layers on the optical characteristics of AlGaAs and quantum wells was investigated using transmission electron microscopy. The results showed that remnants of the InAs often reacted with the AlGaAs after thermal desorption to form InAlGaAs. The resulting InAlGaAs acted as potential wells for carrier recombination. In addition, it dominated the photoluminescence spectrum.

Measurements of the electroreflectance spectra of surface-intrinsic- n+-type-doped GaAs at various bias voltages (Vbias) were conducted. Findings indicate many Franz-Keldysh oscillations (FKOs) above the band-gap energy which were attributed to a uniform electric field (F) in the undoped layer below the surface. No other evidence for the uniformity of F in the undoped layer was observed. Since F can be deduced from the periods of the FKOs, the relations between Vbias an F can be obtained. Thus, the relation confirms the existence of a nearly uniform field in the undoped layer.

Simultaneous mode locking and Q switching is accomplished in a diode-pumped Nd:YV[O.sub.4]/GaAs laser. The average output power is ~2.0 W at 10.6-W absorbed pump power, and the repetition rate of the Q-switched pulse is ~120 kHz. The mode-locked pulse inside the Q-switched pulse has a repetition rate of ~148 MHz, and its average duration is estimated to be ~100 ps. OCIS codes: 140.3480, 140.3540, 140.3580, 140.4050.