P. van der Wal

Terahertz photomixing in high energy oxygen- and nitrogen-ion-implanted GaAs

In this letter, the authors elaborate a detailed study of ion-implanted GaAs terahertz photomixers. The authors implanted several GaAs samples with oxygen and nitrogen ions with energies between 2 and 3MeV and doses ranging from 2×1011to3×1013cm−2. The samples were processed by patterning metal-semiconductor-metal structures on the feed point of self-complementary log-periodic spiral broadband antennas. From dc measurements and analysis of frequency roll-off in the 100GHz–1THz range under variable bias conditions, the authors studied systematically the carrier trapping time, terahertz power, and photocurrent dependence on applied voltage and frequency for the different samples.

Terahertz photonic mixers as local oscillators for hot electron bolometer and superconductor-insulator-superconductor astronomical receivers

A pump experiment of two astronomical heterodyne receivers, a superconductor- insulator-superconductor (SIS) receiver at 450GHz and a hot-electron-bolometer (HEB) receiver at 750GHz, is reported. A low-temperature-grown GaAs metal-semiconductor-metal photonic local oscillator (LO) was illuminated by two near infrared semiconductor lasers, generating a beat frequency in the submillimeter range. I-V junction characteristics for different LO pump power levels demonstrate that the power delivered by the photomixer is sufficient to pump a SIS and a HEB mixer. SIS receiver noise temperatures were compared using a conventional solid-state LO and a photonic LO. In both cases, the best receiver noise temperature was identical (Tsys=170K).

A submillimeter heterodyne receiver for the Kuiper Airborne Observatory and the detection of the 372 μm carbon monoxide line J=7–6 in OMC-1 and W3

A compact heterodyne receiver system used in the Kuiper Airborne Observatory (KAO) is described. Calibration techniques and methods for eliminating standing wave effects are presented.The J=7–6 rotational transition of carbon monoxide was detected in OMC-1 and in W3 with a beam of 5.5′ HPBW.The peak antenna temperature of OMC-1 is 55 K, with the line center at +8±1 kms−1 and FWHM 6.0±0.3 kms−1. The total line flux in our beam is 7.8×10−13 Wm−2. This relatively high value seems to indicate that OMC-1 might be extended over at least several arcminutes in CO (J=7–6).In W3, the peak antenna temperature is 6±2 K, with line center at −42±2 kms−1 and FWHM ∼9 kms−1. The total line flux is 1.5×10−13 Wm−2. W3 thus emits about 50 L⊙ in CO (J=7–6) alone.

Photonic (sub)millimeterwave local oscillators

Optical heterodyne millimeter-wave (mm-wave) generation using traveling-wave photodetectors (TW-PDs) is examined both experimentally and theoretically. Ultrahigh-frequency (110 GHz, 160 GHz and 460 GHz) InP-based 1.55 /spl mu/m TW-PDs were fabricated and employed in experimental set-ups for optical heterodyning. For the first time a 1.55 /spl mu/m photonic sub millimetre-wave (460 GHz) local oscillator (LO) module has been developed and demonstrated.

A 1 GHz bandwidth acousto-optical spectrometer for airborne submillimetre astronomy

A compact modular acousto-optical spectrometer (AOS) has been built for airborne astronomical observations. It has a bandwidth of 992 MHz and a resolution of 1.7 MHz. It is easy to transport and to adjust and provides it own data acquisition and handling system. The AOS was successfully flown on board the Kuiper Airborne Observatory in September 1988 and performed just as well as in the laboratory.

Power Stabilization of the Dual-Mode Laser Using Volume Holographic Gratings

We present a power stabilization method for a dual-mode Ti:Sapphire ring cavity laser. Without stabilization, mode competition caused the output power of the two modes to fluctuate by approximately 10 dB. The power stabilization system, which used volume holographic gratings to monitor the power in each mode, reduced the power fluctuations to less than 3 dB.

A Compact Submillimeter Laser for Airborne Applications

Research on coherent radiation sources in the submillimeter (submm) wavelength region (100 pm - 1 mm, 3 THz - 300 GHz, 100 cm-1 -10 cm-1), operating in a continuous wave (cw) mode led to the development of klystrons, carcinotrons, glow discharge and optically pumped lasers. Whereas klystrons and carcinotrons are tunable over a relatively wide wavelength range, but only useful for wavelengths larger than 300 µm, lasers however can only be operated on discrete transitions but on more than 1000 laser lines in the whole submm region [1]. The advantage of optically pumped submm lasers, compared with the other sources is high output power, good signal to noise ratio and high spectral purity. This paper reports the development of a compact submm laser system, consist- ing of a CO2 pump laser and a submm laser, for astronomical airborne observations [2]. The laser system has passed its first test flights with a NASA science aircraft (Kuiper Airborne Observatory, type C-l4lA, Lockheed) in April 1985. For this application, high mechanical stability and stable operation of the lasers, independent of orientation is required over a flight duration of up to 8 hours. During a research flight, the laser system will be mounted at a 91 cm aperture infrared telescope.