A folded-type integrated-optic spectrum analyzer using butt-coupled chirped grating lenses

A folded-type integrated-optic spectrum analyzer (IOSA) using reflection-type chirped grating lenses butt-coupled to a LiNbO3waveguide Bragg cell is presented. The lenses can be easily fabricated by the well-established planar process, and the IOSA has good performance as well as a reduced device length. The spectrum analyzer function of 4.0 MHz resolution in 95-345 MHz RF frequency range is demonstrated.     

Integrated optical spectrum analyzer with internal gain

The first scanning integrated optical spectrum analyzer (IOSA) with resolution enhancement due to intracavity loss compensation in an amplifying Ti:Er:LiNbO₃-waveguide is reported. The active IOSA of about 1.423 GHz free spectral range has been diode-pumped at λ_p=1479 nm (E_p∥c) slightly below the lasing threshold at 1531 nm (P_p,th≅40 mW). Linear scanning of the cavity resonances has been achieved by driving the phase modulator (U_x≅10.4 V) with a sawtooth voltage. A finesse up to 205 has been achieved at λ_s≅1546 nm     

RF excitation of a flowing gas CO2 waveguide laser

Investigation of an RF excited CO₂ waveguide laser in flowing gas operation is reported. Power extraction of 0.8 W/cm with an efficiency of 10.3% has been achieved. Using W.W. Rigrod's analysis (1965), values of the small-signal gain α₀ and saturation parameter I_s have been determined for different excitation levels and for different pressures of the amplifying medium. The parameters α₀ and I_s, have been determined as 0.6%/cm and 10.4 kW/cm ², respectively, at 125 torr and 100 W/cm³ RF loading power. These values are close to those reported for sealed-off RF CO₂ waveguide lasers with xenon added to the gas mixture     

Integrated acoustooptic modules for interferometric RF spectrum analyzers

An integrated acoustooptic (AO) module that consists of a wideband AO Bragg cell, a wide-angle ion-milled concave Bragg grating lens, and a large-aperture titanium-indiffusion proton-exchange lens has been realized in a y-cut LiNbO/sub 3/ waveguide 1*8*16 mm/sup 3/ in size and used to perform interferometric RF spectrum analysis. This module has provided a bandwidth of 205 MHz centered at 350 MHz and single-tone instantaneous and two-tone, third-order spurious-free dynamic ranges of 50 and 40 dB, respectively, at 1.0 mW of 0.6328- mu m laser power and a drive power of 50 mW per RF signal. A pair of such basic AO modules has been integrated in a common LiNbO/sub 3/ substrate 1*10*16 mm/sup 3/ in size to facilitate measurement of the phase difference, and thus the angle of arrival, of RF signals.<>     

A 500 MHz tunable CO2waveguide laser for optical pumping

A long-pulse CO2waveguide laser is described, which can be single frequency tuned over 500 MHz in about 80 lines. A peak power reaching 125 W at line center and 85 W at the tuning edge in the strongest lines makes the laser ideally suited for optically pumped FIR lasers. New FIR lines have been observed by pumping CH3OH in absorptions located up to 268 MHz from the CO2line center. FIR wavelengths have been measured, identified, and compared to calculations at a level of relative accuracy of5 cdot 10^{-5}.     

Integrated optic strip waveguide phase modulator driven by a SAW

Single-mode integrated optic strip waveguide phase modulators driven by a surface acoustic wave (SAW) are investigated theoretically and experimentally. Evaluating the overlap integral, a good agreement is obtained between measured and theoretical results. Measurements were performed onZY-LiNbO3(z-cut crystal,y-propagating SAW) between 20 MHz and 580 MHz atlambda_{0} = 0.85 mum optical wavelength using Titanium indiffused waveguides. At 9-mW SAW power in an interaction length of 4 mm, optical phase shifts are measured to be 0.32 and 0.112 for TM and TE polarization, respectively, at 21.5 MHz.     

Similarity and scaling in diffusion-cooled RF-excited carbondioxide lasers

The theoretical and experimental study of alpha RF discharges presented in this paper has resulted in the formulation of a set of similarity and scaling laws for diffusion-cooled alpha RF discharge-excited CW waveguide CO₂ lasers. For the first time, the parametric dependencies of the voltage-current-power characteristics of a transverse alpha RF discharge have been investigated over a range of excitation frequencies 100-160 MHz, for gas pressures 40-100 torr and for interelectrode distances 1-3 mm in a typical waveguide CO₂ laser gas mixture (He:N₂Co ₂=3:1:1+5 percent Xe). Relative to dc discharges, the additional scaling law fD=constant is established, and the analysis indicates both high- and low-frequency limits to the operation of practical self-similar laser devices     

An 18-GHz continuous-time Σ-Δ analog-digital converterimplemented in InP-transferred substrate HBT technology

We report an 18-GHz clock-rate second-order continuous-time Σ-Δ analog-digital converter (ADC) implemented using InP-transferred substrate HBTs. Under two-tone test conditions, the ADC achieved 43 dB and 33 dB SNR at signal frequencies of 500 MHz and 990 MHz, respectively. The IC occupied 1.95 mm² die area and dissipated ~1.5 W     

基于新型互补开环谐振器的基片集成波导滤波器

设计了一种新型的互补开环谐振器(Complementary split ring resonators,CSRR),研究了新型CSRR应用在基片集成波导(Substrate integrated waveguide,SIW)时的频率响应。采用该结构设计并制作了两个SIW滤波器,其中心频率分别为5 GHz和6 GHz,带宽分别为800 MHz和2 GHz,设计和实测结果较为吻合。     

A 385–500 GHz SIDEBAND-SEPARATING (2SB) SIS MIXER BASED ON A WAVEGUIDE SPLIT-BLOCK COUPLER

We have developed a 385–500 GHz sideband-separating (2SB) mixer, which is based on a waveguide split-block coupler at the edge of the H-plane of the 508 μm × 254 μm (WR 2.0) waveguide, for the Atacama Large Millimeter/submillimeter Array (ALMA). An RF/LO coupler, which contains an RF quadrature hybrid, two LO couplers, and an in-phase power divider, was designed with the issue of mechanical tolerance taken into account. The RF/LO coupler was measured optically with a microscope and electrically with a submillimeter vector network analyzer. The image rejection ratio (IRR) and the single-sideband (SSB) noise temperature of the receiver using the RF/LO coupler have also been measured. The IRR was found to be larger than 8 dB and typically ～ 12 dB in the 385–500 GHz band. The SSB noise temperature of this receiver is 80 K at the band center, which corresponds to 4 times the quantum noise limit (hf/k) in SSB, and 250 K at the band edges.     

Integrated Optics Acoustooptic Receiver

The recent advances on the research and the applications of the integrated optics acousto-optic spectrum analyzer(IOSA) are reviewed.The operating principle,ar-chitecture,characteristics and technology,and future development of the different re-ceiers are described.     

基于扇形基片集成波导的三频带通滤波器设计

该文提出了一种60°扇形基片集成波导谐振器,然后在谐振器中加载一排金属通孔,对其TM₁₁₀、TM₂₁₀和TM₁₂₀模进行扰动,最后利用扰动后的场模式,在60°扇形基片集成波导谐振器的基础上设计了一款结构紧凑的三频带通滤波器。通过分别引入互补开口环谐振器和源-负载耦合结构,改善了滤波器的频率选择特性。3个通带的中心频率分别为5.61 GHz、7.41 GHz和8.77 GHz,3 dB带宽分别为148 MHz、298 MHz、347 MHz。滤波器的测试与仿真结果基本吻合。     

Monolithically integrated waveguide-MSM detector-HEMT amplifier receiver for long-waveguide lightwave systems

The first demonstration is reported of a long-wavelength receiver that monolithically integrates an InGaAsP waveguide, an InAlAs-InGaAs metal-semiconductor-metal (MSM) detector, and an InAlAs-InGaAs high-election-mobility transistor (HEMT) amplifier. External responsivities in response to a guided signal of 0.43 and 0.5 A/W were recorded, respectively for a 150- and a 300- mu m-long detector integrated with an InGaAsP waveguide. This corresponds to an internal quantum efficiency of about 95% after taking account of the combined external losses such as insertion loss between waveguide and fiber and propagation loss in the waveguide. A pulse response of 200 ps. corresponding to a bandwidth of about 820 MHz, was measured at the output of the HEMT amplifier. The receiver represents a major advance toward achieving high-performance integrated receiving components for long-wavelength lightwave systems.<>     

Hooting modes in a CO2 waveguide laser

CO₂ waveguide lasers `hoot' when, instead of the solitary resonator mode expected from a homogeneously broadened gas laser, two or more resonator transverse modes laser simultaneously on a common laser line. The unwanted mode or modes, even if very faint and present only occasionally, can impede heterodyne measurements where a clean frequency spectrum is required. The authors report measurements of transverse-mode beat frequencies from a small RF-excited CO₂ laser with a hybrid Al/Al₂O₃ square-bore waveguide and plane mirrors; these frequencies alter with mirror tilt by up to 70 MHz mrad^-1. A minimum beat frequency is seen when the laser is well assigned. The authors suggest that a model of the misaligned resonator may help to identify the faint modes responsible for hooting     

Measured propagation characteristics of coplanar waveguide on semi-insulating 4H-SiC through 800 K

Wireless sensors for high temperature industrial applications and jet engines require RF transmission lines and RF integrated circuits (RFICs) on wide bandgap semiconductors such as SiC. In this paper, the complex propagation constant of coplanar waveguide fabricated on semi-insulating 4H-SiC has been measured through 813 K. It is shown that the attenuation increases 3.4 dB/cm at 50 GHz as the SiC temperature is increased from 300 K to 813 K. Above 500 K, the major contribution to loss is the decrease in SiC resistivity. The effective permittivity of the same line increases by approximately 5% at microwave frequencies and 20% at 1 GHz.     

High stability CW waveguide CO2laser for high resolution saturation spectroscopy

We describe a stable waveguide CO2laser for spectroscopic applications. The short term spectral width is less than 10 kHz and a 10^-12flicker floor is reached for the Allan variance. A study of the oscillation frequency versus resonator length demonstrates the major influence of the anomalous index of refraction of the medium. Saturation resonances with a 20 kHz peak-to-peak width have been obtained with a very good signal-to-noise ratio. A complete spectrum of SF6forP(16) at 947.74 cm^-1is given as an example to illustrate the 500 MHz bandwidth of the laser.     

模折射率透镜光学特性的计算分析

本文从传统几何光学原理出发,用光线追迹的方法来计算研究准直光束斜入射到模折射率透镜(MIL)上产生的像差,以及当半导体激光器与波导端射耦合以MIL作为准直透镜时,输出准直光束的发散情况,并探讨MIL在集成光学频谱分析仪(IOSA)中作为准直或会聚透镜的适用性。计算表明MIL在IOSA中作为准直或会聚均是可行的。     

A low-spurious fast-hopping MB-OFDM UWB synthesizer

A frequency synthesizer for the ultra-wide band(UWB)group # 1 is proposed.The synthesizer uses a phase locked loop(PLL)and single-sideband(SSB)mixers to generate the three center frequencies of the first band group by mixing 4224 MHz with ±264 MHz and 792 MHz,respectively.A novel multi-QSSB mixer is designed to combine the function of frequency selection and frequency conversion for low power and high linearity.The synthesizer is fabricated in Jazz 0.18-μm RF CMOS technology.The measured reference spur is as low as-69 dBc and the maximum spur is the LO leakage of-32 dBc.A low phase noise of-110 dBc/Hz @ 1 MHz offset and an integrated phase noise of 1.86°are achieved.The hopping time between different bands is less than 1.8 ns.The synthesizer consumes 30 mA from a1.8 V supply.     

Integrated optical detector array, waveguide, and modulator based on silicon technology

An integrated optical (IO) hybrid circuit consisting of a photodetector array, waveguide, and acousto-optic modulator on a common silicon substrate has been fabricated. This IO hybrid circuit is a major step in the development of a combination optical-electronic processing system. In this device an array of p-n junction photodiodes was fabricated on a 2-in silicon wafer and a 7059 glass waveguide film sputtered over an SiO/SUB 2/ insulating layer on the wafer. Another SiO/SUB 2/ layer was deposited under the transducer electrode. The transducer was a 40-MHz lithium niobate rotated Y-cut crystal. A prism was used to couple in the light beam from a 5 mW He-Ne laser. The guided light beam was directed at one of the diodes in the array and pulsed RF signals were applied to the transducer. Oscillator frequencies of 40 MHz and 120 MHz were separately applied. Modulation depths of greater than 25 percent were produced. The fabrication of the optical guide photodiode and electrical interconnections on a single silicon wafer utilized standard IC fabrication techniques.     

Collinear acoustical TM-TE mode conversion in proton exchangedTi:LiNbO3 waveguide structures

Collinear acoustooptic TM-TE mode conversion is experimentally investigated in proton exchanged Ti:LiNbO₃ optical waveguides. Their birefringence is adjusted by an appropriate annealing to allow phase matching at surface acoustic wave frequencies of about 90 MHz and 180 MHz, respectively. A planar mode converter with an efficiency of up to 90 percent is presented (87 MHz, 175 MHz). Furthermore, a combined acoustical/optical strip waveguide structure is developed as mode converter, leading to strongly reduced power requirements; only 0.3-mW acoustic power is sufficient to achieve a conversion efficiency of 50 percent