Lianping Hou

Subpicosecond Pulse Generation at Quasi-40-GHz Using a Passively Mode-Locked AlGaInAs–InP 1.55-

We report on subpicosecond pulse generation using passively mode-locked laser diodes based on AlGaInAs 1.55-mum strained multiquantum-wells. Without any external pulse compression, the nearly transform-limited Gaussian pulses are generated at the quasi-40-GHz repetition rate with the 700-fs pulse duration.

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Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of ±0.20 nm, corresponding to a tolerance of ±0.032 nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%.

Strained Quantum-Well Laser

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.

High channel count and high precision channel spacing multi-wavelength laser array for future PICs

In this paper, we present an experimental and theoretical study of passive mode-locking in semiconductor Fabry-Pérot, quantum-well, lasers operating at around 1550 nm and producing picosecond pulses at a repetition frequency of 40 GHz. The different regimes that occur as the reverse bias voltage applied to the saturable absorber (SA) section or the bias current injected into the amplifier section are characterized both in the time and frequency/wavelength domains. Our results reveal that the lasers display spectral competition between the gain of the amplifier section and the absorption of the SA, with variations of the lasing wavelength up to 25 nm as the bias conditions are changed. These wavelength variations result from the thermal drift of the SA band-edge due to Joule heating by the generated photocurrent and from the competition between two possible lasing regions placed either at the amplifier gain peak or near the band-edge of the SA. The experimental observations are satisfactorily reproduced and explained in the framework of a Traveling Wave Model complemented by a time-domain description of the semiconductor susceptibility.

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

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.

Spectral Dynamical Behavior in Passively Mode-Locked Semiconductor Lasers

We measured the absorption recovery times in reverse biased AlInGaAs multiple quantum well material designed to emit at around 1.5 μm wavelength. Absorption recovery times as low as 2.5 ps were found at -4V bias, with values below 5 ps consistently found for biases above 3 V. The short absorption recovery times obtained under reverse bias were confirmed by using cross-absorption modulation in the material to demonstrate wavelength conversion of a 10 GHz pulse train, showing both up and down conversion of the incident pulses.

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

We have fabricated 40-GHz passively mode-locked AlGaInAs-InP 1.55- lasers integrated with surface-etched distributed Bragg mirrors. Numerically optimized gratings provide low-scattering losses and accurate wavelength control. The lasers produce 4.46-ps Gaussian pulses with time-bandwidth product of 0.47.

Fast saturable absorption and 10 GHz wavelength conversion in Al-quaternary multiple quantum wells.

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.

Monolithic 40-GHz Passively Mode-Locked AlGaInAs–InP 1.55-

High-power 40 GHz 1.55 μm passively mode-locked surface-etched distributed Bragg reflector lasers monolithically integrated with semiconductor optical amplifiers (SOAs) are reported. These are based on an optimized AlGaInAs/InP epitaxial structure with a three quantum-well active layer and a far-field reduction layer. The device produces near transform-limited sech2 pulses with the shortest measured pulse duration at 3.19 ps, and the narrowest measured radio frequency linewidth at 110 kHz. The highest average output power at ~155 mW with a peak power of >0.6 W was attained from the SOA-end facet while mode-locked. The beam divergences from the SOA side were narrow and symmetric (26.7° × 26.8°), which is highly desirable for butt coupling to a single-mode fiber.

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The monolithic integration of four 10-GHz 1.55- μm AlGaInAs/InP mode-locked surface-etched distributed Bragg reflector lasers with a 4 × 1 multimode-interference optical combiner, a curved semiconductor optical amplifier, and electroabsorption modulator using relatively simple technologies-surface-etched distributed Bragg reflector and quantum-well intermixing-has been demonstrated. Our techniques have the advantage of eliminating crystal regrowth and antireflection coating processes that are required in traditional methods. The four channels can operate separately or simultaneously. They also can be synchronized at the same pulse repetition frequency by the injection mode-locked technique.