Jiaren Liu

A

A passive InAs/InP quantum dot (QD) semiconductor mode-locked laser (MLL) emitting 403-GHz repetition rate pulses with 268- and 563-fs pulse durations is demonstrated experimentally around 1.54 μm. The QD MLL consists of a QD Fabry-Pérot laser and external cavities that include eight fiber Bragg gratings (FBGs). The mode-locking is realized by four-wave mixing in the QD waveguide between the longitudinal modes selected by the FBGs.

C

A multiwavelength laser with maximum signal-to-noise ratio up to 62 dB was demonstrated on the basis of a 461-m-long InAs-InGaAsP quantum-dot waveguide Fabry-Perot cavity chip. It has 24 channels with 0.8-nm channel spacing and 8.0-dB maximum channel intensity nonuniformity over a wavelength range from 1612 to 1632 nm. Its channel spacing irregularity due to linear intracavity waveguide dispersion was also investigated.

-Band InAs/InP Quantum Dot Semiconductor Mode-Locked Laser Emitting 403-GHz Repetition Rate Pulses

A short pulse train with pulsewidth was generated in a quantum dot mode-locked laser (QD MLL). Due to the short dispersion length, it is required to include group-velocity dispersion (GVD) in modeling pulse train generation and evolution from QD MLLs. On the other hand, Kerr effect is also required to consider due to high peak power density in the laser cavity, and its induced self-phase modulation (SPM) also contributes to the pulse evolution. In this paper, a time domain traveling wave model, including the effect of GVD and SPM, combined with rate equations, is established to model the pulse evolution in a single-section QD MLL. It is shown that the pulse evolution calculated by this model is in reasonable agreement with the experiments. The contribution to the pulse evolution by the GVD and SPM impact is discussed.

1.6-

Tunable terahertz beat signal generation is demonstrated by using a C-band InAs/InP quantum-dot (QD) mode-locked laser combined with external cavity of two fiber Bragg gratings (FBGs), where one of the FBGs is tunable in wavelength. Beat signals with ultra-high repetition rates quasi-continuously from 1 to 2.21 THz are observed between the two modes, which are phase-correlated due to intracavity four-wave mixing effect in the QD waveguide.

\mu

We report on a study of terahertz (THz) generation using implanted InGaAs photomixers and multi-wavelength quantum dot lasers. We carry out InGaAs materials growth, optical characterization, device design and fabrication, and photomixing experiments. This approach is capable of generating a comb of electromagnetic radiation from microwave to terahertz. For shortening photomixer carrier lifetime, we employ proton implantation into an epitaxial layer of lattice matched InGaAs grown on InP. Under a 1.55 μm multi-mode InGaAs/InGaAsP quantum dot laser excitation, a frequency comb with a constant frequency spacing of 50 GHz generated on the photomixer is measured, which corresponds to the beats of the laser longitudinal modes. The measurement is performed with a Fourier transform infrared spectrometer. This approach affords a convenient method to achieve a broadband multi-peak coherent THz source.

m Multiwavelength Emission of an InAs–InGaAsP Quantum-Dot Laser

Optical fiber sensors have shown great potentials for aerospace applications. But two issues need to be addressed before these applications can be realized. One is how to reliably implement optical sensors in the air vehicles. The other is the need of compact, low weight sensor interrogation systems. We propose to use planar lightwave circuits (PLC) to address the second issue. In this article, we report some of our results on the development of both echelle diffractive gratings based sensor interrogator and arrayed waveguide gratings based sensor interrogators. Both approaches offer miniaturized solutions for the development of optical fiber sensor interrogation systems.

Modeling of Single-Section Quantum Dot Mode-Locked Lasers: Impact of Group Velocity Dispersion and Self Phase Modulation

Precision laser machining technology was used to cut arrayed waveguide grating (AWG) devices from 6-in wafers by following their complex profiles in a fully automatic way. A substantial cost saving in components manufacturing was achieved by an obtained device-cutting yield of 100%. The profile-cut AWG devices have smooth cutting edges and their optical performances were found unaffected by the cutting. These devices were processed in the subsequent packaging process easily without adding cost. They were proven mechanically stable in their packaging in meeting the telecommunication standards even though they have irregular geometry.

Tunable Terahertz Beat Signal Generation From an InAs/InP Quantum-Dot Mode-Locked Laser Combined With External-Cavity

It is a challenge to simultaneously prevent the fiber ribbons from internal stress in the planar waveguide-based components and protect the ribbons from external stress. We have achieved this by simply incorporating two soft elastomer gaskets into each conventional packaging to compensate the mismatched thermal expansion between the fiber ribbon and packaging case, and fastening the fiber ribbon to the case to transfer their external load away. The involved process was easily implemented at a minimum cost, and the packaged variable optical attenuators and arrayed waveguide gratings were free of internal ribbon stress and able to meet the fiber-handling requirement as specified by Telcordia GR 1209 test.

Terahertz Generation Using Implanted InGaAs Photomixers and Multi-wavelength Quantum Dot Lasers

1x2 and 2x2 optical waveguide directional couplers were fabricated in a silica glass sample by a femtosecond laser and characterized at the wavelength of 1.5 μm. The coupling coefficient was determined by systematically writing series of 1x2 directional couplers. After the process and design optimization, the two types of waveguide directional couplers successfully achieved the coupling ratio of about 3.0 dB with the average IL and PDL 6.55 ± 0.25 dB and 0.28 ± 0.12 dB respectively. The multi-scan writing technique with inter-scan shifts was used to reshape the magnitude and profile of the refractive index change so that excess loss of S bends and the PDL for such couplers were substantially reduced.

Miniaturized optical fiber sensor interrogation systems for potential aerospace applications

We experimentally demonstrated an ultra-broadband supercontinuum source by using two low-cost multimode lasers, Erbium-Yerbium co-doped fiber and highly nonlinear fiber. The bandwidth of the generated broadband source is almost 1100nm, covering from 900 to 2000nm. In addition, the supercontinum source output is smooth and stable.