Tuning Range In Excess Research Articles

A 2.8-to-5.8 GHz harmonic VCO based on an 8-shaped inductor in a 28 nm UTBB FD-SOI CMOS process

A 2.8-to-5.8 GHz harmonic VCO designed in a 28 nm UTBB FD-SOI CMOS process adopts a reconfigurable active core to save power at the lower oscillation frequencies, and to enable a trade-off between power consumption and phase noise at all frequencies. Interference caused by the magnetic coupling to and from the VCO inductor is greatly attenuated by resorting to an inductor in the shape of an 8. Simulations of the magnetic coupling between an 8-shaped inductor and a reference inductor show a reduction in magnetic coupling as high as 44 dB, depending also on size, orientation, and shape of the reference inductor. The UTBB FD-SOI CMOS process is instrumental to achieve a tuning range in excess of one octave at low power consumption. The VCO operates from 0.9 V and has a figure-of-merit of 186---189 dBc/Hz, depending on the oscillation frequency and the configuration of the oscillator core. The active area of the VCO is 380 ? 700 µm.

High power burst-mode optical parametric amplifier with arbitrary pulse selection

We present results from a unique burst-mode femtosecond non-collinear optical parametric amplifier (NOPA) under development for the optical - x-ray pump-probe experiments at the European X-Ray Free-Electron Laser Facility. The NOPA operates at a burst rate of 10 Hz, a duty cycle of 2.5% and an intra-burst repetition rate of up to 4.5 MHz, producing high fidelity 15 fs pulses at a center wavelength of 810 nm. Using dispersive amplification filtering of the super-continuum seed pulses allows for selectable pulse duration up to 75 fs, combined with a tuning range in excess of 100 nm whilst remaining nearly transform limited. At an intra-burst rate of 188 kHz the single pulse energy from two sequential NOPA stages reached 180 µJ, corresponding to an average power of 34W during the burst. Acousto- and electro-optic switching techniques enable the generation of transient free bursts of required length and the selection of arbitrary pulse sequences inside the burst.

All-Optical Tuning of WGMs in Microspheres Made of Er/Yb Codoped Optical Fiber

All-optical, pump-assisted, thermal tuning of high-Q whispering-gallery mode (WGM) resonances of microspheres is demonstrated. The microspheres were made of an Er/Yb codoped single-mode silica optical fiber. The pump light absorbed by the active ions heats the microsphere, which leads to the shift of the resonances. A tuning range in excess of 2 nm in the C-band is achieved. The presence of active ions is restricted to the core of the microsphere. The WGM fields, which are confined in a region close to the surface of the microsphere, do not overlap with the dopant. Thus, high-Q resonances (>10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> ) are achieved, as in pure silica microspheres, even at optical wavelengths within the absorption bands. We explored the use of the microsphere as a photonic scanning receiver for RF signals.

Design of a Beam Switching/Steering Butler Matrix for Phased Array System

A compact broadband 8-way Butler matrix integrated with tunable phase shifters is proposed to provide full beam switching/steering capability. The newly designed multilayer stripline Butler matrix exhibits an average insertion loss of 1.1 dB with amplitude variation less than ±2.2 dB and an average phase imbalance of less than 20.7° from 1.6 GHz to 2.8 GHz. The circuit size is only 160 × 100 mm2, which corresponds to an 85% size reduction compared with a comparable conventional microstrip 8-way Butler matrix. The stripline tunable phase shifter is designed based on the asymmetric reflection-type configuration, where a Chebyshev matching network is utilized to convert the port impedance from 50 ? to 25 ? so that a phase tuning range in excess of 120° can be obtained from 1.6 GHz to 2.8 GHz. To demonstrate the beam switching/steering functionality, the proposed tunable Butler matrix is applied to a 1 × 8 antenna array system. The measured radiation patterns show that the beam can be fully steered within a spatial range of 108°.

Purely axial compression of fiber Bragg gratings embedded in a highly deformable polymer

We demonstrate a tuning device for fiber Bragg gratings with a wavelength tuning range in excess of 65 nm. A purely axial tuning technique using a highly deformable polymer molded in a cylinder shape is used to embed a fiber Bragg grating and to achieve a wavelength tuning range from 1551.7 to 1485.5 nm. The tuning curve is highly linear with a tuning rate of 9.6 nm for every percent of applied strain. The insertion losses of the device, the variations of the full width at half maximum, and the stability of the Bragg wavelength over a working day have been studied and shown to be less than 0.02 dB, 0.14, and 0.2 nm, respectively.

Single grating period quantum cascade laser array with broad wavelength tuning range

A distributed feedback quantum cascade laser array emitting at λ∼10 µm is reported. Utilising a ridge width dependence on emission wavelength, the array of laser ridges exhibited a tuning range in excess of 230 nm over the temperature range of 140 to 380 K. Singlemode operation with sidemode suppression ratios of ≥25 dB and a combined tuning coefficient of −0.1 cm−1 K−1 are demonstrated.

单模可调谐近/中红外垂直腔面发射激光器

Single-mode, long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the near- to mid-infrared covering the wavelength range from 1.3 to 2.3 are presented. This wide spectral emission range opens applications in gas sensing and optical interconnects. All these lasers are monolithically grown in the InGaAlAs-InP material system utilizing a buried tunnel junction (BTJ) as current aperture. Fabricated with a novel high-speed design with reduced parasitics, bandwidths in excess of 10 GHz at 1.3 and 1.55 µm have been achieved. Therefore, the coarse wavelength division multiplexing (CWDM) wavelength range of 1.3 to 1.6 µm at 10 Gb/s can be accomplished with one technology. Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated. One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning. Micro-electro-mechanical system (MEMS) tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity. All these devices feature continuous-wave (CW) operation with typical single-mode output powers exceeding 1 mW. The operation voltage is around 1-1.5 V and power consumption is as low as 10-20 mW. Furthermore, we have also developed VCSELs based on GaSb, targeting at the wavelength range from 2.3 to 3.0 µm. The functionality of tunable diode laser spectroscopy (TDLS) systems is shown by presenting a laser hygrometer applying a 1.84-µm VCSEL.

Enhanced self-heterodyne performance using a Nd-doped ceramic YAG laser

Two-frequency operation in ceramic neodymium-doped yttrium aluminium garnet is demonstrated for 1.064μm operation with a self-heterodyne beat-frequency tuning range in excess of 1.5GHz. A 6dB improvement of the peak-beat strength is seen in the ceramic material over that of similar crystalline Nd:YAG lasers. Experimentally, the ceramic host material is shown to have substantially higher polarization mode coupling constant, C=0.72±0.05, compared to crystalline Nd:YAG, C=0.16±0.05. The peak-beat strength is related to mode coupling. In general the Nd:ceramic YAG dual-frequency laser offers superior performance as a photonic-based radio-frequency source over Nd:YAG.

Advancing the Optical Feed Back Concept: Grating Enhanced External Cavity Diode Laser

We present theoretical and experimental investigations on a new optical feedback concept for single mode diode lasers. It is based on the optical feedback from a resonant external cavity coupled to the diode laser through the 1st order diffraction of a grating. With a single mode diode laser operating at 852 nm we demonstrate a short term line width of less than 60 kHz, an overall tuneability in excess of 36.4 nm and a continuous tuning range in excess of 45 GHz, both at constant diode temperature.

TUNABLE MICROELECTROMECHANICAL CAPACITOR WITH WIDE TUNING RANGES

The objective of the paper presented here is to develop and demonstrate a MEMS silicon-based tunable capacitor for RF communications application. The tunable capacitor is made of single crystal silicon based on silicon-on-insulator (SOI) technology, and that has a continuous tuning range in excess of 300%. The electrical capacitance model will be provided here in details to demonstrate tuning characteristic and RF performance of tunable capacitor.

Extended tuning range in sampled grating DBR lasers

The authors demonstrate, for the first time, successful implementation of a distributed Bragg reflector laser with two sampled grating mirrors, which they previously predicted should give tuning range in excess of 50 nm. This device uses a uniform grating pitch throughout the structure, and relies on the same fabrication technology as a standard DBR laser. Initial results show 57 nm of mathematical tuning at 1.475 mu m with side-mode suppression ratio (SMSR)>30 dB over much of the tuning range. The observed change in operating wavelength versus mirror currents along with below threshold spectra agree with theoretical expectations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wide-Band Varactor-tuned Coaxial Oscillators

An experimental investigation into the effects of package and circuit reactances on wide-band varactor-tuned oscillators is described. The results are used to design an X-band Gunn coaxial oscillator with a tuning range in excess of 3 GHz. It is shown that the stray reactance, junction capacitance, and bond-wire inductance affect the varactor tuning characteristics. The characteristics are conveniently displayed by the reflection phase variation with tuning voltage and frequency. A general theory for wide-band varactor-tuned oscillators is presented which is related to the impedance characteristics. These results are used to design three coaxial varactor-tuned oscillators. The first two oscillators are series arrangements while the third oscillator is a parallel arrangement. A simple circuit technique is used to improve the tuning range of each arrangement. This technique is shown to increase the coupling to the varactor diode and decrease the oscillator Q by reactance compensation.

Broad-Band Varactor-Tuned Impatt-Diode Oscillator (Short Papers)

A varactor-tuned IMPATT-diode oscillator with a continuous and monotonic tuning bandwidth of 27 percent and a potential tuning range in excess of 40 percent is described. The results of a computer program which optimizes the tuning bandwidth of the equivalent circuit of the voltage-controlled oscillator (VCO) are presented. The VCO consists of two varactors located symmetrically on each side of an IMPATT diode all mounted in a ridged waveguide with two matched outputs into 50-Omega coaxial. Experimental results on bandwidth, power output, frequency linearity, and FM noise are presented.