IEEE Journal of Quantum Electronics

Two different treatments of spontaneous emission in distributed-feedback (DFB) lasers were found in the literature, but adequate explanations for the different treatments were not found. Using an approach that allows comparison of the two different treatments of spontaneous emission, we show that the different treatments can lead to different spectral predictions. The difference in spectral predic... View full abstract»

We describe the design, fabrication, and performance of a five-element quarterwave-shifted distributed feedback laser array with monolithically integrated spot size converters intended for use as a multiple-wavelength source in dense wavelength-division telecommunications systems. Facet power in excess of 10 mW with less than 150 mA bias and longitudinal side mode suppression greater than 40 dB we... View full abstract»

For pt. I, see ibid., vol. 36, p. 430, April 2000. The waveform manipulation technique known as temporal imaging can expand or compress signals in time while maintaining the shape of their envelope profiles. The temporal imaging system is analogous to that of its spatial counterpart, with dispersive propagation performing the role of diffraction and quadratic phase modulation in time acting as a "... View full abstract»

An experimental and theoretical investigation of how the polarization mode competition and beat frequency of Er-doped fiber distributed-feedback lasers depend on perturbations such as localized transverse forces, back reflections, or changes in pump polarization is reported. Good agreement between the experiments and a comprehensive theoretical model is obtained. Use of a dual-polarization laser a... View full abstract»

Investigations have been performed on harmonic generation from solid-vacuum interfaces using a 2.2-ps 1054-nm laser pulse at maximum intensities of /spl sim/2/spl times/10/sup 17/ W/spl middot/cm/sup -2/. It is found that the divergence of the harmonics gradually increases at intensities between I/spl lambda//sup 2/=2/spl times/10/sup 15/ and 2/spl times/10/sup 16/ W/spl middot/cm/sup -2//spl midd... View full abstract»

We present the concept of a novel resonant-cavity LED design where a symmetric resonant cavity (RC) is added to the outcoupling reflector. Because of the peculiar characteristics of the resulting mirror, these so-called RC/sup 2/LED's have a much higher extraction efficiency into a limited NA as compared to conventional RCLED designs. View full abstract»

Efficiencies are calculated for quantum-dot apertured-microcavity light-emitting diodes. Although the maximum efficiency depends strongly on the quantum-dot inhomogeneous broadening, greater than 20% efficiency is calculated for a small-sized apertured microcavity, even for an inhomogeneous linewidth as large as 30 meV. The efficiency can be increased to 40% if the inhomogeneous linewidth is reduc... View full abstract»

Singlewall carbon nanotube (SWNT) suspensions have been shown to be good optical limiters mainly because of their nonlinear scattering properties. In this paper, we report on a pump-probe experiment coupled with emission measurements for SWNT's in two solvents (water and chloroform). Time-resolved probe transmission with a pump at 1064 nm and a CW probe at 633 nm permits one to associate optical l... View full abstract»

We report on experimental results and the numerical modeling of the compensation of nonlinear self-focusing effects occurring in a high-power Nd:glass laser system at intensities above 1 GW/cm/sup 2/. A GaAs wafer with a negative nonlinear refractive index was used for the cancellation of the accumulated phase difference along the beam direction in a nonlinear medium (B integral). A numerical mode... View full abstract»

The photocurrent dark decay in photorefractive materials is theoretically analyzed by using two different dynamical approaches-namely, the shallow traps and electron-hole transport models. The analysis is based on experimental results that show a double exponential decay of the photocurrent with short pulsed or continuous excitation. Expressions for the photocurrent amplitudes and decay times have... View full abstract»

The effect of grating dispersion on pulse evolution in a photorefractive self-pumped phase conjugator is analyzed. The broadening factors and the time-dependent phases of self-pumped phase-conjugate pulses of unchirped and chirped Gaussian pulses are obtained. When the grating dispersion and the angular dispersion cancel the material dispersion, the self-pumped phase-conjugate pulse has a minimum ... View full abstract»

Wannier-Stark localization of heavy holes and the associated refractive index changes in a strongly coupled GaAs-Al/sub 0.75/Ga/sub 0.25/As three-quantum-well structure have been investigated. Electroabsorption has been measured for TE polarization and the results compared with simulations performed by the exciton Green's function method to reveal the dominant contributions to the differential abs... View full abstract»

We present a theoretical investigation of the spectral properties of spontaneous emission in semiconductor optical amplifiers. We use an extended (3/spl times/3) transfer matrix formalism to derive in the spectral domain an expression for the total longitudinally averaged internal field, which is valid regardless of the levels of optical input and bias current. The material parameters are saturate... View full abstract»

To characterize semiconductor lasers, it is often required to measure parameters such as the quasi Fermi-level separation, intrinsic optical loss, the position of the gain peak, and gain and absolute refractive index spectra. For these measurements, there are many different techniques available, but they neglect to take into account the dispersion of refractive index and cannot be used to extract ... View full abstract»

The effect of both n-type and p-type modulation doping on multiple-quantum-well (MQW) laser performances was studied using gas-source molecular beam epitaxy (MBE) with the object of the further improvement of long-wavelength strained MQW lasers. The obtained threshold current density was as low as 250 A/cm/sup 2/ for 1200-/spl mu/m-long devices in n-type modulation-doped MQW (MD-MQW) lasers. A ver... View full abstract»

A two-section cavity device has been used to measure gain spectra and waveguide losses of a GaAs-based quantum cascade laser. The device operates at 8.9 /spl mu/m and optical confinement is obtained by means of Al-free cladding layers. We investigated the gain characteristics in a spectral window of /spl sim/60 meV and up to 200 K. For current densities ranging from 1 to 8 kA/cm/sup 2/, we report ... View full abstract»

Using a top-contact window, we have observed emission from a direct-gap monitor layer placed at the interface between the p-cladding and contact layers of an AlGaInP laser diode when driven under forward bias, thereby providing direct evidence for minority carrier (electron) leakage in these devices. We have further shown that the leakage is due to both drift and diffusion and, using pulsed optica... View full abstract»

A high-power diode-pumped Nd:YAG laser oscillating at a wavelength of 1.319 /spl mu/m is reported. A 122-W CW laser beam with an M2 factor of 35 has been achieved with an optical efficiency of 19.6%. The lasing characteristics, including thermal lensing, at 1.319 /spl mu/m are compared with those at 1.06 /spl mu/m. Under lasing conditions, the focal length of thermal lensing at 1.319 /spl mu/m dec... View full abstract»

The thermal lens is a critical issue, particularly in high-power diode-pumped solid-state laser rods. A self-adjusting scheme for compensation of the thermally induced lens is presented. The requirements for such an element and its influence on the resonator are discussed. With an appropriate compensating element and a suitable resonator design, constant beam parameters are expected to be achieved... View full abstract»