Wide Frequency Tuning Range Research Articles

Magnetic induced dichroism and frequency stabilization of violet-blue diode lasers on gallium atomic transitions

We study the magnetic-field-induced dichroism on a sample of gallium neutral atoms created in a hollow cathode lamp and describe a method for robust stabilization of violet-blue diode lasers tuned on gallium atomic transitions for an atom nanofabrication experiment. We compare the experimental dichroic signals with theoretical simulations obtained by the solving of the exact atom-field interaction Hamiltonian. We find excellent agreement when considering the magnetic field shielding from the hollow cathode. This method allows for a wide range of frequency tuning, modulation-free locking, and long-term stability of external-cavity diode lasers. From analysis of a square root Allan variance we have achieved a stability of 1 MHz at 1-s average time.

Variable bandwidth, wide tunable frequency, voltage tuned filter

This article discusses the development of an electronically tuned filter capable of a wide tunable frequency range and simultaneous 3-dB bandwidth variations at any frequency within its tuning rang...

Frequency entrainment for micromechanical oscillator

We demonstrate synchronization of laser-induced self-sustained vibrations of radio-frequency micromechanical resonators by applying a small pilot signal either as an inertial drive at the natural frequency of the resonator or by modulating the stiffness of the oscillator at double the natural frequency. By sweeping the pilot signal frequency, we demonstrate that the entrainment zone is hysteretic and can be as wide as 4% of the natural frequency of the resonator, 400 times the 1/Q∼10−4 half-width of the resonant peak. Possible applications are discussed based on the wide range of frequency tuning and the power gain provided by the large amplitude of self-oscillations (controlled by a small pilot signal).

Generation and transmission of millimeter-wave data-modulated optical signals using an optical injection phase-lock loop

Generation and transmission of millimeter-wave data-modulated optical signals is presented using an optical injection phase-lock loop (OIPLL). Millimeter-wave signal generation is demonstrated with wide locking range, 30-GHz low phase noise level, -93 dBc/Hz, and a wide frequency tuning range, 4-60 GHz generation demonstrated using optical injection locking only, verified by using OIPLL in the 26-40 GHz range. The OIPLL is also used to transmit error-free 140-Mb/s amplitude shift keying and 68-Mb/s differential phase-shift keying (DPSK) modulated millimeter-wave signals over up to 65 km of uncompensated standard singlemode fiber. The DPSK system uses reference frequency modulation, eliminating the need for optical amplification.

Variable bandwidth, wide tunable frequency, voltage tuned filter

This article discusses the development of an electronically tuned filter capable of a wide tunable frequency range and simultaneous 3-dB bandwidth variations at any frequency within its tuning range. Varactor-tunable filters are designed using high-dielectric, soft-substrate material for printed resonators as well as also high-Q ceramic resonators, and their test data are compared. Greater than 50% tuning range with low insertion loss at a center frequency in the L and S frequency bands is demonstrated with a 4:1 change in 3-dB bandwidth—30 to 120 MHz for printed resonators and 14 to 46 MHz for ceramic resonators. The concept of tuning a filter's 3-dB bandwidth with voltage is demonstrated and the effect of the bandwidth tuning elements on the tunable filter performance is discussed. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 64–72, 2004.

CONTINUOUSLY TUNABLE EXTENDED CAVITY DIODE LASER AT 780 nm FOR HIGH RESOLUTION SPECTROSCOPY

In this communication we have investigated and compared the tuning abilities of an ECDL system, using a grating in Littrow configuration, depending on the laser diode (LD) used. We have achieved experimentally a wide continuous frequency tuning range by applying translation-rotational movement of the grating together with appropriate injection current correction. The fluorescence spectrum of Rb in the vicinity of 780 nm has been recorded in an external absorption cell. The wide mode-hop free frequency tuning gave us the possibility to reach exactly the maximum of each fine component of the Rb D2 line. By scanning the applied magnetic field strength, sub-natural width resonance (SNWR), with FWHM in the kHz range, have been observed in the fluorescence signal and in the transmitted output power. Such resonance is very appropriate for measuring weak magnetic fields.

A 20-GHz InP-HBT voltage-controlled oscillator with wide frequency tuning range

This paper presents the design and implementation of a 20-GHz-band differential voltage-controlled oscillator (VCO) using InP heterojunction-bipolar-transistor process technology. Aimed at 20- or 40-Gb/s fiber-optic applications, the design is based on a single-stage feedback amplifier with no intentional L or C. The salient features of the proposed VCO are wide frequency tuning range compared to LC oscillators, and low power consumption and transistor count compared to ring-oscillator counterparts. The implemented VCO has an adjustable frequency range from 13.75 to 21.5 GHz and provides two complementary outputs. Total power consumption at 18.6 GHz is 130 mW, while the phase noise is -90.0 dBc/Hz measured at 1-MHz offset frequency.

BWO-Characterization of Materials and Devices at Frequencies 100-1000 GHz.

ABSTRACTWe have developed multipurpose spectral technique for amplitude and phase measurements at frequencies 100–1000 GHz based on the use of backward wave oscillators (BWOs) as sources of probing radiation. It utilizes to the utmost all the remarkable advantages of BWOs such as high radiation intensity, monochromaticity, polarization, as well as high speed and wide range of frequency tuning. Extremely simple and flexible open-space measurement geometries are used. The developed technique seems to be the most appropriate and promising for the reliable, precise and mass characterization of materials and devices at millimeter-submillimeter waves.

GaAs HEMT monolithic voltage-controlled oscillators at 20 and 30 GHz incorporating Schottky-varactor frequency tuning

This paper describes the design and fabrication of fully monolithic voltage-controlled oscillator (VCO) circuits using a combined GaAs high electron-mobility transistor (HEMT) and Schottky-varactor diode process. To the authors' knowledge, this is the first time a process of this type has been used for VCO fabrication. Three VCO designs with similar circuit topology, but two different operating frequencies and resonator types, were investigated to compare their relative performance. Two approaches to the integrated resonator were tried: coupled and single microstrip lines. The single resonator approach resulted in better power efficiency, while the coupled resonator was found to provide a wider frequency tuning range and lower phase noise.

A 20-GHz-band subharmonically injection-locked oscillator MMIC with wide locking range

A monolithic subharmonically injection-locked oscillator (ILO) with wide frequency tuning range using a shunted varactor diode inserted to the oscillation loop is presented. A 20-GHz-band ILO is fabricated that achieves the wide injection locking range of more than 700 MHz at each subharmonic factor up to 32. In addition, the phase-noise degradation rate of the ILO against the subharmonic factor is close to 6 db/oct. The ILO configuration is extremely suitable for realizing low cost and low-phase-noise millimeter-wave monolithic microwave integrated circuit (MMIC) sources.

Wide-tuning range Si bipolar VCOs based on three-dimensional MMIC technology

The first completely integrated silicon (Si) bipolar junction transistor (BJT) voltage-controlled oscillators (VCOs), based on three-dimensional (3-D) monolithic-microwave integrated-circuit (MMIC) technology are presented in this paper. The 3-D MMIC technology offers the use of reactive matching in circuit design as well as GaAs MMIC construction and expands the operation frequency of Si MMICs. Two types of VCO MMICs using 0.5-/spl mu/m Si BJTs are presented and demonstrated. Both exhibit a very wide frequency tuning range in the 5- and 6-GHz bands. The former offers the frequency tuning range of 33% using the base-emitter conductance operation of the BJT, which works like a varistor with a large ratio. Furthermore, the oscillation frequency is remarkably linear against the controlled base bias. To confirm the wide-tuning ability of the proposed VCO at higher frequencies, a 7-GHz-band VCO is fabricated on the same Si masterslice array used for the 5-GHz-band VCO. It achieves a 28% tuning range from 5.53 to 7.09 GHz at the collector bias of 2 V. The latter, whose frequency is controlled by a varactor diode, also offers a wide tuning range from 5.15 to 6.75 GHz. The phase noise achieved ranges from -95 dBc/Hz to -117 dBc/Hz at 1-MHz offset frequency over the tuning range of 1.6 GHz (best phase noise performance is -90.5 dBc/Hz at 100 kHz). Measured results show that 3-D MMIC Si VCO's can he developed that yield frequencies above 7 GHz.

A design framework for low power analog filter banks

We detail the design of multiresolution analog filter banks, linear models of cochlear function, with power dissipation being a prime engineering constraint. We propose that a reasonable goodness criterion is the information rate through the system, per watt of power dissipated. Speech applications requiring filter banks with a wide frequency tuning range, from 20 Hz to 20 kHz, and low power consumption make the transconductance-C integrator in subthreshold CMOS the preferable integrator structure. As an example, the dynamic range of a lowpass filter is computed and subsequently used to design a filter bank that models faithfully cochlear micro-mechanics. The power consumption of the entire filter bank is computed from analytical expressions and is estimated as 355 nW, at 68 kb/s overall information rate at the output of the system.

Optical coherence domain reflectometry by synthesis of coherence function with nonlinearity compensation in frequency modulation of a laser diode

Optical coherence domain reflectometry (OCDR) is proposed by synthesis of the coherence function for high-spatial-resolution diagnoses of optical systems and waveguide devices. By changing the output frequency of a laser diode using its direct frequency modulation characteristic, the coherence function having the shape of a delta function is synthesized. In the basic experiments, the reflectivity distribution is measured successfully by sweeping the position of the peak. Nonlinearity compensation in the direct frequency modulation is experimentally demonstrated in order to improve the resolution. A three-electrode DFB laser diode with wide-frequency tunable range is introduced as the light source. A spatial resolution of 2-4 mm in air is demonstrated. The measurement range flexibility of this method is confirmed in the experiments.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spatial characteristics of pump and "Stokes" beams under conditions of resonant stimulated Raman scattering in NH3

An investigation was made of the spatial characteristics of the pump and beams under conditions of resonant stimulated Raman scattering by NH3 in a multipass cell. In spite of the large difference between the wavelengths of the pump and Stokes radiation, some similarity was observed between the output dimensions of their beams. It was found that, in a wide range of frequency tuning, resonant self-interaction influenced strongly the propagation of CO2 laser radiation and Stokes radiation in a multipass cell.

Resonant stimulated Raman scattering in NH3characterized by pump radiation depletion and a wide frequency tuning range

Concurrent resonance stimulated Raman scattering (RSTRS) of radiation from a CO2 laser was observed in NH3 for the Gs(5, 0) → 1ν2s(5, 0) transition. Four new lasing lines were observed in the wavelength range 67 μm. The tuning range in the far infrared was 4.5 cm−1. The power of infrared radiation reached 2 MW for a quantum efficiency of the process 36%. Depletion of the pump radiation, time dependence of the process, and forward–backward asymmetry of RSTRS were observed. A study was made of the difference between the RSTRS characteristics for one and three passes through a multipass cell. The stimulated Raman scattering thresholds were different for linear and circular pump polarizations.

Resistance of GaAS Varactor Diodes for TV Tuners

Gallium arsenide varactor diodes have been extensively used in microwave applications because of high Q. But few papers have reported the diodes for UHF use, 1,2) although strongly requested to realize low noise TV tuners satisfying with the FCC noise figure requirement. In order to cover wide tuning frequency range as is used in TV UHF broadcasting band with varactor diodes, hyperabrupt diodes are needed. Hyper-abrupt GaAs diodes have been manufactured by a double epitaxial growth technique.1,2) These diodes for microwave use are commercially available.

Orotron—An electronic oscillator with an open resonator and reflecting grating

The results are presented from a study of the orotron, a new electronic generator of the millimeter and submillimeter wavebands with a wide range of frequency tuning. An open resonator with a grating on one of its mirrors is used as the oscillatory system. The device is excited by passing an electron beam over the grating.