A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.

Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

R EIEW A R TCLE Abstract As an emerging topic, photonic-assisted microwave measurements with distinct features such as wide frequency coverage, large instantaneous bandwidth, low frequencydependent loss, and immunity to electromagnetic interference, have been extensively studied recently. In this article, we provide a comprehensive overview of the latest advances in photonic microwave measurements, including microwave spectrum analysis, instantaneous frequency measurement, microwave channelization, Doppler frequency-shift measurement, angle-of-arrival detection, time–frequency analysis, compressive sensing, and phase-noise measurement. A photonic microwave radar, as a functional measurement system, is also reviewed. The performance of the photonic measurement solutions is evaluated and compared with the electronic solutions. Future prospects using photonic integrated circuits and software-defined architectures to further improve the measurement performance are also discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.201600019

Photonics for microwave measurements

By doping an organic compound functioning as an electron donor (hereinafter referred to as donor molecules) into an organic compound layer contacting a cathode, donor levels can be formed between respective LUMO (lowest unoccupied molecular orbital) levels between the cathode and the organic compound layer, and therefore electrons can be injected from the cathode, and transmission of the injected electrons can be performed with good efficiency. Further, there are no problems such as excessive energy loss, deterioration of the organic compound layer itself, and the like accompanying electron movement, and therefore an increase in the electron injecting characteristics and a decrease in the driver voltage can both be achieved without depending on the work function of the cathode material.

Light Emitting Device

Microwave measurement refers to the acquisition of parameters of a microwave signal or the identification of properties of an object via microwave-based approaches. Thanks to the broad bandwidth and high speed provided by modern photonics, microwave measurement in the optical domain can provide better performance in terms of bandwidth and speed which may not be achievable using traditional, even state-of-the-art electronics. In this tutorial, techniques for photonics-based broadband and high-speed microwave measurement are discussed with an emphasis on the system architectures for microwave signal parameter measurement and object property identification. Emerging technologies in this area and possible future research directions are also discussed.

Photonics-Based Broadband Microwave Measurement

Integration of the whole mode-locked laser onto a single piece of semiconductor offers a number of advantages, including total elimination of optical alignment processes, improved mechanical stability, and the generation of short optical pulses at much higher repetition frequencies. Semiconductor laser processing technologies were used to implement the colliding-pulse mode-locking (CPM) scheme, which is known to effectively shorten the pulses and increase stability, on a miniature monolithic semiconductor cavity. The principles of and recent progress in monolithic CPM quantum-well lasers are reviewed. >

Monolithic colliding-pulse mode-locked quantum well lasers

A coherent optical RF channelizer has been constructed and characterized. The optical channelizer is based on a free-space optical diffraction grating, and utilizes coherent optical heterodyne detection to translate all of the frequency channels to a common intermediate frequency (IF). The designed optical channelizer has a 1-GHz channel spacing, and a nominal 5-GHz IF and can offer an instantaneous bandwidth greater than 100 GHz. The channelizing receiver has been characterized for its frequency response, crosstalk, and spur-free dynamic range, and the results are in a good agreement with the theoretical values.

/pdf/characterization-of-a-coherent-optical-rf-channelizer-based-1cmnwomt79.pdf

Characterization of a coherent optical RF channelizer based on a diffraction grating

CW injection locking of mode-locked semiconductor lasers has been experimentally demonstrated. The phases of the mode-locked frequency comb are shown to be coherent with that of the master CW laser. The pulsewidth of the mode-locked laser remains almost unchanged (<2 ps) for a broad range of injection power (-28 to -12 dBm). Pulling of the entire mode-locked frequency comb by 400 MHz has been demonstrated. The coherent multifrequency source can be used as a local oscillator comb for coherent optical channelizers for ultrawide-band RF signals.

/pdf/cw-injection-locking-of-a-mode-locked-semiconductor-laser-as-4b7njwymyn.pdf

CW injection locking of a mode-locked semiconductor laser as a local oscillator comb for channelizing broad-band RF signals

A waveguide ( 10 ) is provided having a two-dimensional optical wavelength Bragg grating ( 20 ) embedded within a semiconductor laser medium ( 16 ). More particularly, the waveguide ( 10 ) includes an active region ( 16 ) sandwiched between n-doped and p-doped cladding layers ( 14, 22 ). The two-dimensional Bragg grating ( 20 ) is formed in the active region ( 16 ). Upper and lower electrodes ( 24, 26 ) are defined on opposite sides of the cladding layers ( 14, 22 ) to complete the waveguide structure ( 10 ). The two-dimensional grating ( 20 ) provides simultaneous frequency selective feedback for mode control in both the longitudinal and lateral directions.

High power single mode semiconductor lasers and optical amplifiers using 2D Bragg gratings

An injection locking system for lasers. In particular, a signal from a master laser is phase modulated and injected into a slave laser. The phase difference φ is maintained at zero by way of a phase locked loop. By maintaining the phase difference φ at zero, the frequency drift is compensated by maintaining the frequency within a predetermined locking range.

Stabilization of injection locking of CW lasers

We demonstrate single mode operation of laser diode cavities up to 200|iim wide using 2-D Bragg gratings for simultaneous longitudinal and lateral mode control.

Robert Lodenkamper

Papers

Characterization of a coherent optical RF channelizer based on a diffraction grating

CW injection locking of a mode-locked semiconductor laser as a local oscillator comb for channelizing broad-band RF signals

High power single mode semiconductor lasers and optical amplifiers using 2D Bragg gratings

Stabilization of injection locking of CW lasers

Large spatial mode, single frequency semiconductor lasers using two dimensionalgratings