Schottky Diode Frequency Multipliers Research Articles

Optical injection locking of a THz quantum-cascade VECSEL with an electronic source.

Optical injection locking of a metasurface quantum-cascade (QC) vertical-external-cavity surface-emitting laser (VECSEL) is demonstrated at 2.5 THz using a Schottky diode frequency multiplier chain as the injection source. The spectral properties of the source are transferred to the laser output with a locked linewidth of ∼1 Hz, as measured by a separate subharmonic diode mixer, and a locking bandwidth of ∼300 MHz is achieved. The large locking range is enabled by the microwatt power levels available from modern diode multipliers. The interplay between the injected signal and feedback from external reflections is studied and demonstrated to increase or decrease the locking bandwidth relative to the classic locking range depending on the phase of the feedback.

Corrections to “Design and Fabrication of Broadband Hybrid GaAs Schottky Diode Frequency Multipliers” [Dec 13 4442-4460

The block diagram shown in Fig 33 of the above-named paper [ibid., vol. 61, no. 12, pp. 4442–4460, Dec. 2013] is incorrect. Instead of series resonators, it should contain parallel resonators. A corrected version is provided here as Fig. 1. In the continuous text of the above paper [p. 4451, col. 2, line 38] it reads series resonator, which is incorrect. It should read half-wave MSL parallel resonator.

Design of Dual-Mode Frequency Multiplier With Schottky Diodes

This work presents a dual-mode Schottky diode frequency multiplier, which produces second and third harmonic simultaneously with low spurs and high efficiency. The dual-mode multiplier is designed based on the traditional balanced frequency tripler, except that the second harmonic is extracted from the circle of the diode pair, and dc bias could be applied from the second harmonic output path. A prototype pumped by about 5 GHz signal has been fabricated and tested. The measured second harmonic conversion efficiency is 7.1%–8.9% at frequencies from 9 to 10.1 GHz with spurs lower than <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 22 dBc, while the third harmonic conversion efficiency is 1%–1.3% at frequencies from 13.5 to 15.15 GHz with spurs lower than <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$-$</tex></formula> 27 dBc.

Physics-Based Design and Optimization of Schottky Diode Frequency Multipliers for Terahertz Applications

Planar Schottky diode frequency multipliers are by far the most employed devices for local oscillator (LO) power generation at terahertz frequencies. In order to push up to the limit the available LO power at terahertz frequencies, the use of accurate physics-based simulation tools is highly necessary to develop multiplier circuits with the highest performance. This paper investigates the potential capabilities of Schottky multipliers for LO power generation up to 2.4 THz by means of an in-house computer-aided design tool that combines harmonic balance techniques with an accurate physics-based numerical model of the semiconductor device. According to numerical simulation results, a 32-μW LO power could be theoretically achieved with a 2.4-THz LO chain at room temperature from a 150-mW W-band solid-state LO source. This demonstrates that there is still a broad margin for the improvement of state-of-the-art terahertz LO power sources.

Variable-wavelength frequency-domain terahertz ellipsometry

We report an experimental setup for wavelength-tunable frequency-domain ellipsometric measurements in the terahertz spectral range from 0.2 to 1.5 THz employing a desktop-based backward wave oscillator source. The instrument allows for variable angles of incidence between 30 degrees and 90 degrees and operates in a polarizer-sample-rotating analyzer scheme. The backward wave oscillator source has a tunable base frequency of 107-177 GHz and is augmented with a set of Schottky diode frequency multipliers in order to extend the spectral range to 1.5 THz. We use an odd-bounce image rotation system in combination with a wire grid polarizer to prepare the input polarization state. A highly phosphorous-doped Si substrate serves as a first sample model system. We show that the ellipsometric data obtained with our novel terahertz ellipsometer can be well described within the classical Drude model, which at the same time is in perfect agreement with midinfrared ellipsometry data obtained from the same sample for comparison. The analysis of the terahertz ellipsometric data of a low phosphorous-doped n-type Si substrate demonstrates that ellipsometry in the terahertz spectral range allows the determination of free charge-carrier properties for electron concentrations as low as 8x10(14) cm(-3).