D.C. Scott

60 GHz sources using optically driven heterojunction bipolar transistors

Millimeter wave sources at 60 GHz have been demonstrated using optically driven heterojunction bipolar transistors configured as photodetectors. Two techniques were used to optically generate the millimeter waves; the mixing of two cw lasers and the mode locking of a semiconductor laser. The millimeter wave power generated from these two configurations was radiated into free space using integrated planar twin‐dipole antennas and heterodyne detected with signal‐to‐noise ratios ≳40 dB. As part of these experiments, the dc optical gains and quantum efficiencies of the heterojunction bipolar transistor photodetectors were determined.

High-power high-frequency traveling-wave heterojunction phototransistors with integrated polyimide waveguide

A high-power high-speed phototransistor has been demonstrated using a traveling-wave (TW) structure with an integrated polyimide optical waveguide. In our configuration, optical power transfer is distributed along the length of the device via leaky mode coupling of light from the polyimide waveguide to the active region of the phototransistor. The TW electrode design allows for an electrically long structure while maintaining high bandwidths. Due to the increased absorption volume, the optical power handling capabilities of the TW-heterojunction phototransistors (TW-HPTs) are improved over that of conventional lumped-element HPT detectors. The experimental results show no saturation of the fundamental at 60 GHz up to 50 mA of DC photocurrent.

Optically generated 60 GHz millimeter waves using AlGaAs/InGaAs HEMTs integrated with both quasi-optical antenna circuits and MMICs

Continuously tunable 49-67 GHz millimeter wave radiation has been generated using optical mixing in AlGaAs/InGaAs HEMTs integrated with both quasi-optical antenna circuits and multistage MMIC amplifiers. Using these systems, microwatt levels of millimeter wave power have been generated. A quantitative study of the signal strength versus bias, polarization, and light intensity was performed. In addition, the millimeter waves were modulated by applying an RF signal (< GHz) to the FET gate. Using this technique, tunable electrical sidebands were added to the optically generated 60 GHz carrier, thus providing a method of transmitting information.<<ETX>>

Generation of millimeter-wave radiation by optical mixing in FETs integrated with printed circuit antennas

The generation of continuous wave 60-GHz millimeter wave radiation from FETs integrated with planar antennas using optical mixing is demonstrated. The radiation was propagated through narrowband quasi-optical Fabry-Perot filters and heterodyne detected in a second FET antenna structure. A schematic representation of the experimental arrangement is given. The response of a tunable Fabry-Perot interferometer is measured. In addition to spectroscopic applications, this transmitter/receiver system demonstrates the feasibility of having optically fed arrays of millimeter-wave sources.<<ETX>>

High power, high frequency traveling wave heterojunction phototransistors with integrated polyimide waveguide

A high power, high speed phototransistor has been demonstrated using a traveling wave structure with an integrated polyimide optical waveguide. In our configuration, optical power transfer is distributed along the length of the device via leaky mode coupling of light from the polyimide waveguide to the active region of the phototransistor. The traveling wave electrode design allows for an electrically long structure while maintaining high bandwidths. Due to the increased absorption volume, the optical power handling capabilities of the TW-HPT are improved over that of conventional lumped element HPT detectors. The experimental results show no compression of the fundamental at 60 GHz up to 50 mA of DC photocurrent.

High performance long-wavelength velocity-matched distributed photodetectors for RF fiber optic links

Improved performance of InP-based long wavelength velocity-matched distributed photodetector (VMDP) with metal-semiconductor-metal photodiodes is experimentally demonstrated. A 3-dB bandwidth of 13 GHz and an external quantum efficiency of 0.57 A/W have been achieved.

Microwave phase conjugation using arrays of nonlinear optically pumped devices

Phase conjugation is a technique for reversing both the direction of propagation and the overall phase factor of an incoming wave. Up to date, most developments have concentrated on the optical regime due to the availability of nonlinear materials and power density restrictions. The extension of phase conjugation techniques to microwave frequencies has been explored using mixing elements with antennas [Cutler et al., 1963]. In this work, we report the use of optical signals as carriers of the microwave pump signal. This optical injection technique is the key to making simple, viable, low cost microwave phase conjugation arrays and nonlinear microwave surfaces.

Microwave phase conjugation using antenna coupled nonlinear optically pumped surfaces

An effort to extend phase conjugation techniques to microwave frequencies using optically injected active nonlinear elements is reported. Initial results were obtained using PIN diodes as detectors and microwave mixers as the nonlinear medium. Our current work is based upon optically injected HBTs as nonlinear mixing elements in conjunction with planar antenna arrays.<<ETX>>

60 GHz sources using optically driven HBTs

Millimeter-wave sources at 60 GHz have been demonstrated using optically driven heterojunction bipolar transistors (HBTs) configured as photodetectors. Two techniques were used to optically generate the millimeter waves: the mixing of two continuous wave lasers and the mode locking of a semiconductor laser. The millimeter-wave power generated from these two configurations was radiated into free-space using integrated planar twin dipole antennas and heterodyne detected with signal to noise ratios>40 dB. As part of these experiments, the DC optical gain and quantum efficiency of the HBT photodetectors were determined.<<ETX>>

Use Of Picosecond Optical Pulses And FETs Integrated With Printed Circuit Antennas To Generate Millimeter Waves

Millimeter wave radiation has been generated from FETs and HEMTs, integrated with printed circuit antennas, and illuminated with picosecond optical pulses. Modulation of the millimeter waves was achieved by applying a swept RF signal to the transistor gate. Using this technique, tunable electrical sidebands were added to the optically generated carrier providing a method of transmitting information and doing high resolution spectroscopy. Heterodyne detection demonstrated that the system continuously generated tunable radiation, constrained by the high gain antenna, from 45 to 75 GHz. ECENT experiments have shown that optoelectronic