A proposed ultra low-noise optical receiver for 1.55 μm applications

A high-sensitivity optical receiver based on InP/InGaAs superlattice avalanche photodiode (SL-APD) followed by an InGaAs MESFET transimpedance pre-amplifier has been proposed for operation in 1.55 m wavelength region. The proposed optical receiver may be realised in the hybrid integrated circuit form. The low excess-noise factor of the SL-APD significantly reduces the value of minimum detectable optical power and improves the sensitivity of the over all receiver. The proposed receiver has been analysed theoretically. The results of computation show that the device has a high transimpedance gain (60 dB-ohm) with a bandwidth of 11 GHz for a photodetector capacitance of 110 fF. The sensitivity of the receiver has been found to be (–27.3d Bm) at operating bit rate of 15 Gb/s for a bit-error-rate of 10^–9. The performance of the receiver can be optimised in respect of transimpedance gain, bandwidth and sensitivity by following guidelines provided in this paper. The proposed photoreceiver outperforms the existing receivers based on p-i-n/FET or conventional APD/FET photoreceivers.     

Superlattice avalanche photodiodes for optical communications

This paper reviews the research into and development trends to date of high-speed high-sensitivity semiconductor superlattice (SL) avalanche photodiodes (APDs) for use in 1.3 to 1.55m wavelength optical communications. We focus on three types of SL-APDs based on an InAlGaAs-well/InAlAs-barrier structure. The first is an InAlGaAs/InAlAs polyimide-coated mesa-structure SL-APD with a high gain-bandwidth product of over 120GHz and a low multiplied dark current of a few tens of nano-amperes. Its reliability has been measured to be over 105h at 50°C. The second is a planar-structure SL-APD with a new titanium-implanted guard-ring; this structure has a longer lifetime than the mesa structure. The third is a large-receiving-area SL-APD integrated with a monolithic lens for eye-safety 1.5m wavelength optical measurement systems.     

A superconducting tunnel junction receiver for 345 GHz

In this paper we discuss the design, fabrication, and testing of a quasiparticle tunnel junction receiver for use at 345 GHz. The design employs small area Nb/Nb-oxide/PbInAu edge junctions in order to keep the device capacitance small and maintain a modest value for R_NC. For optimura noise performance and beam properties the mixer is contained in a waveguide mounting structure. Our best sensitivity was obtained at 312 GHz where we measured a double sideband (DSB) noise temperature of 275 K. Noise temperatures of 400 K (DSB) or better were obtained out to 350 GHz.     

A Low-Noise 230 GHz SIS Receiver for Radio Astronomy Employing Untuned Nb/AlOx/Nb Tunnel Junctions

A heterodyne receiver based on a 1/3 reduced height rectangular waveguide SIS mixer with two mechanical tuners has been built for astronomical observations of molecular transitions in the 230 GHz frequency band. The mixer used an untuned array (R_nC_j3, R_n70 ) of four Nb/AIOx/Nb tunnel junctions in series as a nonlinear mixing element. A reasonable balance between the input and output coupling efficiencies has been obtained by choosing the junction number N=4. The receiver exhibits DSB (Double Side Band) noise temperature around 50 K over a frequency range of more than 10 GHz centered at 230 GHz. The lowest system noise temperature of 38 K has been recorded at 232.5 GHz. Mainly by adjusting the subwaveguide backshort, the SSB (Single Side Band) operation with image rejection of 15 dB is obtained with the noise temperature as low as 50 K. In addition, the noise contribution from each receiver component has been studied further. The minimum SIS mixer noise temperature is estimated as 15 K, pretty close to the quantum limit v/k11 K at 230 GHz. It is believed that the receiver noise temperatures presented are the lowest yet reported for a 230 GHz receiver using untuned junctions.     

Analysis of sensitivity and low-frequency intensity noise characteristics of Bragg reflector lasers induced by reflected light

An analysis of the sensitivity and low-frequency intensity noise characteristics of Bragg reflector lasers is given. It is found that Bragg reflector lasers have increased sensitivity to reflected light for low grating coupling strength (l) and is similar to that of Fabry-Perot lasers except for highl values. Also, the intensity noise can be reduced by operating the device at high injection level.     

The Development of a Dual Channel SIS Receiver of Trao Telescope

We developed a low noise dual channel receiver with 100GHz and 150GHz band, which is used to make the simultaneous observation with two bands. The SIS mixers are used in both bands. The constructed dewar for the receiver has a performance with a vacuum of 10^–8torr and a temperature of 4.2K. The receiver noise temperature is 50K(DSB) for 100GHz band and 80K(DSB) for 150GHz band, respectively. In order to achieve the simultaneous observations, the quasioptical system is precisely designed, and also evaluated by measurements in the laboratory. The relative pointing offset between two bands is 3. We have observed the various sources using the receiver since October 1998.     

180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIOx/Nb tunnel junctions

We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm² Nb/AlO _x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an end-loaded tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.     

A low-noise 492 GHz SIS waveguide receiver

In this paper we discuss the design and performance of an SIS waveguide receiver which provides low noise performance from 375 to 510 GHz. At its design frequency of 492 GHz the receiver has a double sideband noise temperature of 172 K. By using embedded magnetic field concentrators, we are able to effectively suppress Josephson pair tunneling. Techniques for improving receiver performance are discussed.     

A lownoise 665 GHz SIS quasi-particle waveguide receiver

We report recent results on a 565–690 GHz SIS heterodyne receiver employing a 0.36µm² Nb/AlO _x /Nb SIS tunnel junction with high quality circular non-contacting backshort and E-plane tuners in a full height waveguide mount. No resonant tuning structures have been incorporated in the junction design at this time, even though such structures are expected to help the performance of the receiver. The receiver operates to at least the gap frequency of Niobium, 680 GHz. Typical receiver noise temperatures from 565–690 GHz range from 160K to 230K with a best value of 185K DSB at 648 GHz. With the mixer cooled from 4.3K to 2K the measured receiver noise temperatures decreased by approximately 15%, giving roughly 180K DSB from 660 to 680 GHz. The receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii.     

Low noise 80–115 GHz quasiparticle mixer with small Nb/Al-Oxide/Nb tunnel junctions

Millimeter-wave characterization of a heterodyne receiver using (2 m²) Nb/Al-Ox/Nb Superconducting-Insulator-Superconducting (SIS) junctions arrays is reported. The fabrication of the Nb/Al-Ox/Nb SIS junction arrays as a heterodyne mixer is described. The leakage current of these junctions is below 2A at 4.2K and unmeasurable at 2.5K. The receiver gave a noise temperature Double Side Band (DSB) between 63K and 187K over the frequency range 80 to 115 GHz at the first conversion peak. The results are comparable to those obtained with SIS receivers using well researched lead junctions. Contrary to the lead junctions, our mixer using all Nb junctions have proven remarkably stable with respect to thermal cycling, characteristics which are required for space applications. To our knowledge, this is the most reliable low noise receiver operating in this frequency range.     

P‐type tin‐oxide thin film transistors for blue‐light detection application

We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (I_light/I_dark) of 8.2 × 10³ at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.

     

Receivers for optical communications: A comparison of avalanche photodiodes with PIN-FET hybrids

The effects of photodiode bulk leakage current and amplifier noise on receiver sensitivity are analysed using a model described previously [4]. The sensitivity of a receiver using a PIN photodiode can be greatly improved by employing a high-performance microwave FET in the input stage, to the point where its remaining technical disadvantage in comparison with a silicon APD receiver at 800–900 nm may be offset by economic and operational attractions. In systems operating at the optimum transmission wavelength beyond 1.1 m, the PIN-FET hybrid receiver may offer better technical performance than an APD receiver.     

A 210–280 GHz sis heterodyne receiver for the James Clerk Maxwell Telescope part I: Design and performance

We describe the design and performance of a 210–280 GHz SIS heterodyne receiver built for use on the Maxwell Telescope. The mixer utilises a lead alloy SIS tunnel junction, mounted in 41 reduced height rectangular waveguide, and is tuned with a backshort in 21 reduced height guide. The receiver has a receiver noise temperature of <200K (DSB) across the RF band from 210–270 GHz, with a best noise temperature measured in the laboratory of 113K (DSB) at 231 GHz. A prototype version of this receiver was successfully operated on the telescope in May 1989. By direct intercalibration with a Schottky diode receiver we deduced a best receiver noise temperature of 140K (DSB) at 245 GHz. Discrepancies between this figure and that derived from broad band thermal load calibration are discussed in the accompanying paper (Little et al., 1992, this issue).     

230 and 492 GHz low noise sis waveguide receivers employing tuned Nb/AlOx/Nb tunnel junctions

We report results on two full height waveguide receivers that cover the 200–290 GHz and 380–510 GHz atmospheric windows. The receivers are part of the facility instrumentation at the Caltech Submillimeter Observatory on Mauna Kea in Hawaii. We have measured receiver noise temperatures in the range of 20K–35K DSB in the 200–290 GHz band, and 65–90K DSB in the 390–510 GHz atmospheric band. In both instances low mixer noise temperatures and very high quantum efficiency have been achieved. Conversion gain (3 dB) is possible with the 230 GHz receiver, however lowest noise and most stable operation is achieved with unity conversion gain.A 40% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner full height waveguide mixer block. The tuned Nb/AlO _x /Nb tunnel junctions incorporate an end-loaded tuning stub with two quarter-wave transformer sections to tune out the large junction capacitance. Both 230 and 492 GHz SIS junctions are 0.49µm² in size and have current densities of 8 and 10 kA/cm² respectively.Fourier Transform Spectrometer (FTS) measurements of the 230 and 492 GHz tuned junctions show good agreement with the measured heterodyne waveguide response.     

激光位置探测器的角位移测量精度分析

作为激光光斑位置探测器,象限探测器和位敏探测器被广泛应用于激光光斑跟踪、监控、位置检测和定位等领域。对这两种探测器的角位置测量精度进行了探讨,分析了影响精度的主要噪声源,推导出两者的角位移精度表达式,并通过计算进行了模拟。结果显示,两者的测量精度决定于信号的信噪比,且随作用距离的增加而降低;象限探测器的角位移测量精度明显高于位敏探测器。在忽略背景光噪声的情况下,象限探测器的精度约为位敏探测器的40倍。     

Dual-channel sis receivers for the iram Plateau de Bure Interferometer

The five antennas of the Plateau de Bure Interferometer have been instrumented with dual-channel receivers in the 3 mm and 1 mm bands. Polarisation diplexing allows simultaneous observations in the two bands. Each receiver has ambient and cryogenic calibration loads, and one receiver is equipped with a beam switching chopper for total power flux measurements. Typically the receiver noise temperatures are<50 K in both the 3 mm band and the 1 mm band. Initial observations show that at 115 GHz the sensitivity is doubled compared to the previous receivers, and high quality fringes have been obtained at 230 GHz. Preliminary experiments show that the receiver stability is good enough to correct atmospheric phase variations by monitoring the fluctuations in atmospheric emission at 225 GHz. VLBI fringes have been detected between one 15-m antenna and the IRAM 30-m antenna in Spain.     

An approach to enhance the receiver sensitivity with SOA for optical communication systems

In this paper, we investigate an SOA (semiconductor optical amplifier) preamplifier structure by optimizing the carrier lifetime in order to reduce the amplified spontaneous emission (ASE) noise and crosstalk, with adequate gain increase. This proposed SOA optical preamplifier has no need of optical alignment and antireflection coating. This structure of SOA eliminates the need of optical filter, and exhibits large tolerance to the input light wavelength. The receiver sensitivity is investigated for single and multi channel transmission links. The received power of − 50.34 dBm is observed at bit error rate (BER) 10^− 12 for 10 Gb/s with PIN receiver. Further, the impact of gain, amplified spontaneous emission power and gain variation for different carrier lifetime with input power for OOK system is illustrated. The proposed SOA has constant gain of 30.06 dB up to gain saturation for carrier lifetime 0.18 ns. It is predicted that low value of carrier lifetime suffers less from ASE noise.     

Pulsed millimeter wave fourier transform microwave spectrometer

An improved pulsed microwave spectrometer for the detection of rotational transitions in gaseous molecules in the frequency range of 130–150 GHz is described. It incorporates a tunable Fabry-Perot cavity and a low noise superneterodyne receiver for the detection of the molecular emission signals. The molecules are excited by /2 pulses provided by a high efficiency frequency doubler which is pulse modulated at an IF frequency of 1.4 GHz.     

Escape driven by strongly correlated noise

We consider the colored-noise-driven archetypal bistability dynamics of the Ginzburg-Landau type. The focus is on the stationary behavior and the problem of escape from metastable states. The deterministic flow of the underlyingtwo-variable Fokker-Planck process is studied as a function of the noise correlation time . As a main result we find that the separatrix exhibits a cusp at asymptotically large noise color. The stationary probability is evaluated approximately (unified colored noise approximation) and compared with numerical exact results. The stationary probability forms the key input in the evaluation of the rate of escape. At very strong noise color, the escape path closely follows a nodal line, passing through the corresponding stable node. The asymptotic result for the escape rate at large is compared with exact calculations for the lowest, nonvanishing eigenvalue.