Passive mode-locking in semiconductor lasers with saturable absorbers bandgap shifted through quantum well intermixing

Passive mode-locking in semiconductor lasers in a Fabry–Perot configuration with a bandgap blueshift applied to the saturable absorber (SA) section has been experimentally characterized. For the first time a fully post-growth technique, quantum well intermixing, was adopted to modify the material bandgap in the SA section. The measurements showed not only an expected narrowing of the pulse width but also a significant expansion of the range of bias conditions generating a stable train of optical pulses. Moreover, the pulses from lasers with bandgap shifted absorbers presented reduced chirp and increased peak power with respect to the nonshifted case

High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator

We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB

High Extinction Ratio Polarization Selective TE/TM Bragg Gratings Filters on Silicon-on-insulator

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High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator

We report on the design and fabrication of TE and TM polarization selective Bragg grating filters in the form of sinusoidal perturbations on the waveguide sidewall and etched holes on the top of the waveguide, respectively. Combining the two geometries on a silicon-on-insulator waveguide resulted in Bragg grating filters with high extinction ratios of approximately 60 dB

Ultrashort Q-switched pulses from a passively mode-locked distributed Bragg reflector semiconductor laser

A compact semiconductor mode-locked laser (MLL) is presented that demonstrates strong passive Q-switched mode-locking over a wide range of drive conditions. The Q-switched frequency is tunable between 1 and 4 GHz for mode-locked pulses widths around 3.5 ps. The maximum ratio of peak to average power of the pulse-train is >120, greatly exceeding that of similarly sized passively MLLs

Ultrafast pulse generation in semiconductor lasers

Integrated semiconductor laser devices are presented as extremely compact generators of ultra-short pulse trains. Control is demonstrated on a wide range of emission parameters including wavelength, pulse duration, repetition rate and emitted power. All device geometries require simple drive electronics, consisting of only constant current injection and reverse bias voltage control

High accuracy transfer printing of single-mode membrane silicon photonic devices

A transfer printing (TP) method is presented for the micro-assembly of integrated photonic devices from suspended membrane components. Ultra thin membranes with thickness of 150nm are directly printed without the use of mechanical support and adhesion layers. By using a correlation alignment scheme vertical integration of single-mode silicon waveguides is achieved with an average placement accuracy of 100±70nm. Silicon (Si) μ-ring resonators are also fabricated and show controllable optical coupling by varying the lateral absolute position to an underlying Si bus waveguide

Passive mode-locking in semiconductor lasers with saturable absorbers bandgap shifted through quantum well intermixing

Passive mode-locking in semiconductor lasers in a Fabry-Perot configuration with a bandgap blueshift applied to the saturable absorber (SA) section has been experimentally characterized. For the first time a fully post-growth technique, quantum well intermixing, was adopted to modify the material bandgap in the SA section. The measurements showed not only an expected narrowing of the pulse width but also a significant expansion of the range of bias conditions generating a stable train of optical pulses. Moreover, the pulses from lasers with bandgap shifted absorbers presented reduced chirp and increased peak power with respect to the nonshifted case

X-Band Acquisition Aid Software

The X-band Acquisition Aid (AAP) software is a low-cost acquisition aid for the Deep Space Network (DSN) antennas, and is used while acquiring a spacecraft shortly after it has launched. When enabled, the acquisition aid provides corrections to the antenna-predicted trajectory of the spacecraft to compensate for the variations that occur during the actual launch. The AAP software also provides the corrections to the antenna-predicted trajectory to the navigation team that uses the corrections to refine their model of the spacecraft in order to produce improved antenna-predicted trajectories for each spacecraft that passes over each complex. The software provides an automated Acquisition Aid receiver calibration, and provides graphical displays to the operator and remote viewers via an Ethernet connection. It has a Web server, and the remote workstations use the Firefox browser to view the displays. At any given time, only one operator can control any particular display in order to avoid conflicting commands from more than one control point. The configuration and control is accomplished solely via the graphical displays. The operator does not have to remember any commands. Only a few configuration parameters need to be changed, and can be saved to the appropriate spacecraft-dependent configuration file on the AAP s hard disk. AAP automates the calibration sequence by first commanding the antenna to the correct position, starting the receiver calibration sequence, and then providing the operator with the option of accepting or rejecting the new calibration parameters. If accepted, the new parameters are stored in the appropriate spacecraft-dependent configuration file. The calibration can be performed on the Sun, greatly expanding the window of opportunity for calibration. The spacecraft traditionally used for calibration is in view typically twice per day, and only for about ten minutes each pass

Transfer Printing of Photonic Nanostructures to Silicon Integrated Circuits

Optical systems require the integration of technologies fabricated on different materials. We use a transfer printing technique to integrate pre-processed III-V, polymer and silicon membrane devices onto passive optical circuits with nano-metric positional accuracy