Jehan Akbar

Low divergence angle and low jitter 40 GHz AlGaInAs/InP 1.55 μm mode-locked lasers

We demonstrate a novel (to the best of our knowledge) 40 GHz passively mode-locked AlGaInAs/InP 1.55 μm laser with a low divergence angle (12.7°×26.3°), timing jitter of 1.2 ps (10 kHz-100 MHz), and a radio frequency linewidth of 25 kHz.

Narrow linewidth laterally coupled 1.55 μm AlGaInAs/InP distributed feedback lasers integrated with a curved tapered semiconductor optical amplifier

We present a laterally coupled 1.55 μm AlGaInAs/InP distributed feedback laser monolithically integrated with a curved tapered optical amplifier, providing an output power of 210 mW with single transverse and longitudinal mode operation exhibiting a record low linewidth of 64 kHz.

AlGaInAs/InP Monolithically Integrated DFB Laser Array

The monolithic integration of four 1.50-μm range AlGaInAs/InP distributed feed-back lasers with a 4 × 1 multimode-interference optical combiner, a curved semiconductor optical amplifier and an electroabsorption modulator using relatively simple technologies-sidewall grating and quantum well intermixing-has been demonstrated. The four channels span the wavelength range of 1530-1566 nm and can operate separately or simultaneously. The epitaxial structure was designed to produce a far field pattern at the output waveguide facet, which is as small as 21.2°× 25.1°, producing a coupling efficiency with an angled-end single mode fiber at twice that of a conventional device design.

Photodetachment of Di-atomic Negative Ion H 2 − near a Surface

We describe the effects of plane surface on the photo-detached electron spectra from H−2. A z-polarized laser is used for the detachment of electrons. The detached electron flux and photodetachment cross section are derived. There exists strong dependence on the distance of the H−2 from the surface and also on the separation of atomic centers of H−2. The results show strong oscillations for smaller values of distances, whereas for larger values the oscillating structure disappears.

CWDM source based on AlGaInAs/InP monolithically integrated DFB laser array.

The monolithic integration of four 1.5 μm range AlGaInAs/InP distributed feedback lasers with a 4×1 multimode-interference optical combiner, a curved semiconductor optical amplifier, and an electro-absorption modulator using relatively simple technologies--sidewall grating and quantum well intermixing--has been demonstrated. The four channels span the wavelength range of 1530 to 1566 nm with a channel spacing of 12 nm. The epitaxial structure was designed to produce a far-field pattern as small as 21.2°×25.1°, producing a coupling efficiency with an angled-end single-mode fiber at twice that of a conventional device design.

10-GHz AlGaInAs/InP 1.55-

We present a 10-GHz 1.55-μm passively mode-locked laser based on a novel AlGalnAs/InP epitaxial structure with a three-quantum-well active layer incorporating a passive far-field reduction layer. The device generated 1.06 ps pulses with a state-of-art timing jitter value of 194 fs (4-80 MHz), and a radio-frequency linewidth of 2 kHz, while demonstrating a low divergence angle (14.7° × 27.3°) with a twofold butt coupling efficiency to a flat cleaved single-mode fiber, compared to conventional five-quantum-well mode-locked lasers.

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The photodetachment of a hydrogen negative ion (H−) near a partially reflecting surface with a spherical shape is investigated by a theoretical imaging method. Analytical expressions for the detached electron flux and total photodetachment cross section are derived. It is found that two parameters, i.e. curvature radius rc and reflection parameter K, control the photodetachment spectra. Furthermore, these parameters can be used for the classification, identification and revelation of minor details like curvature of different types of surfaces.

m Passively Mode-Locked Laser With Low Divergence Angle and Timing Jitter

High output power 40 GHz 1.55 μm passively mode-locked surface-etched distributed Bragg reflector (DBR) lasers with monolithically integrated semiconductor optical amplifiers are reported. These are based on an optimized AlGaInAs/InP epitaxial structure with a three quantum well active layer and an optical trap layer. The device produces near transform limited Gaussian pulses with a pulse duration of 3.3 ps. An average output power during mode-locked operation of 130 mW was achieved with a corresponding peak power of >1 W.

Detached Electron Spectra from H− near a Partially Reflecting Spherical Surface

A monolithic ~1.55-μm colliding-pulse mode-locked AlGaInAs/InP laser with a three-quantum-well active layer incorporating a passive far-held reduction layer has been demonstrated. The device emits pulses at 162 GHz, with a pulsewidth of 0.98 ps, a pulse energy of 0.13 pJ, and a time-bandwidth product of 0.52, while demonstrating a low divergence angle (12.7° × 26.3°) with a twofold improvement in butt coupling efficiency to a flat cleaved single-mode fiber, compared to the conventional mode-locked lasers.

High power (130 mW) 40 GHz 1.55 μm mode-locked distributed Bragg reflector lasers with integrated optical amplifiers

We report on the design and experimental evaluation of AlGaInAs/InP multiquantum well epistructures for mode-locked emission at 1.5 μm. We show that mode-locked lasers fabricated on an optimized three quantum well active region with a low optical confinement factor deliver pulses with increased peak power and stability over a much wider biasing range than those fabricated using a standard five quantum well design. Sonogram measurements indicate that sub-ps symmetrical pulses with a substantially reduced linear blue chirp are generated up to nearly three times the laser current threshold.