Frequency-shifting submillimeter single-sideband receiver

A single sideband (SSB) receiver has been developed and implemented for use with a submillimeter sideband generator. While the sideband generator emits both an upper and lower sideband, and even some unshifted laser radiation, the receiver responds to only one sideband. The operator of the system can choose which sideband to receive. Rejection of the undesired signal is accomplished through selective frequency shifting coupled with the use of a commercially available single-sideband microwave mixer.     

A 275–370 GHz Receiver Employing Novel Probe Structure

We present the results of the development of a 275–370 GHz, fixed-tuned double sideband (DSB) receiver based on superconductor-insulator-superconductor (SIS) junction mixer. The mixer block uses a full height rectangular waveguide and employs a novel radial-like probe structure with integrated bias-T. The measured uncorrected receiver noise temperature is 30–50 K corresponding to about 2–3 quantum noise across the full frequency band with an IF from 3.8 to 7.6 GHz. The mixer is to be used on the Atacama Pathfinder EXperiment (APEX) submillimeter telescope in Chile.     

A single-sideband optical balanced mixed

An optical single-sideband mixer, operating at 6328 Å and utilizing two balanced heterodyne mixers, has been constructed. The sideband suppression ratio was measured to be typically about 25 dB and an optimal ratio of 54 dB was achieved.     

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 Broad-Band Low-Noise Schottky Diode Full-Height Waveguide Mixer from 80 to 115 GHz

The RF matching problem in the input circuit of the mm-wavelength whisker contacted Schottky diode mixer is studied. The experimental results, obtained on the 3mm wavelength mixer mounts in the broad band of frequencies from 80 to 115 GHz are presented. It is shown that advantage in the receiver noise temperature may be realized by the use of a full-height instead of 1/4-reduced-height waveguide because of reduction loss in the mixer input circuit even beginning from the 3mm-wavelength. With a full-height waveguide mixer the double sideband (DSB) receiver noise temperature is 300 divided by 350K over the 85 to 110 GHz band. Input bandwidth of the fullheight waveguide mixer (cap delta f _S/f _SO greater than 30%) is equal to 1/2-and close to 1/4-reduced-height waveguide mixers.     

Fourier synthesis of 9.6-GHz optical-pulse trains by phase locking of three continuous-wave semiconductor lasers

Fourier synthesis of optical-pulse trains based on optical phase locking of three cw semiconductor lasers has been demonstrated by use of a semiconductor optical amplifier as a four-wave mixer. The temporal waveforms of the pulse trains were directly observed at a repetition rate of 9.6 GHz by a fast sampling oscilloscope. The FM sideband heterodyne technique was employed to realize a stable homodyne optical phase-locked loop.     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^–17 W/Hz^1/2 at 324 GHz and 5.0×10^–17 W/Hz^1/2 at 693 GHz.     

A 40 GHz band SIS receiver using Nb/Al?AlOx/Nb array junctions

A 40 GHz band SIS mixer receiver has been built using Nb/Al–AlOx/Nb array junctions and a 4.3 K closed cycle helium refrigerator. The minimum conversion loss of the mixer is 2±1 dB and the single sideband receiver noise temperature (T_RX (SSB)) is as low as 110±10 K at 36 GHz. T_RX (SSB) is almost constant in the IF bandwidth of 600 MHz. The mixer saturation level is as high as 15 nW, which is comparable to the injected LO power.Nobeyama Radio Observatory (NRO), a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open for outside users.     

Noise temperature distribution of superconducting hot electron bolometer mixers

We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5) telescope. By evaluating the double sideband(DSB) receiver noise temperature(Trec) across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points, a broad optimal bias region has been observed, illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point. The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components, whose transmissions have been measured by a time-domain spectroscopy. The corrected noise temperature distribution shows a frequency independence relation. The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated, the bath temperature has limited effect on the lowest receiver noise temperature until 7 K, however the optimal bias region deteriorates obviously with increasing bath temperature.     

Heterodyne mixing at 70 GHz with superconductor-insulator-superconductor tunnel junctions

A laboratory heterodyne receiver working at 70 GHz was built up using superconductor-insulator-superconductor tunnel junction as mixing element. Single sideband conversion loss L_C as low as 1.92±0.23 and mixer noise temperature T_M of less than 100 K have been achieved while local oscillator pump power is 4·10^–8W.     

Strong Squeezing of Duffing Oscillator in a Highly Dissipative Optomechanical Cavity System

In the conventional scheme of generating strong mechanical squeezing by the joint effect between mechanical parametric amplification and sideband cooling, the resolved sideband condition is required so as to overcome the quantum backaction heating. In the unresolved sideband regime, to suppress the quantum backaction, a χ⁽²⁾ nonlinear medium is introduced to the cavity. The result shows that the quantum backaction heating effect caused by unwanted counter-rotating term can be completely removed. Hence, the strong mechanical squeezing can be obtained even for the system far from the resolved-sideband regime.     

All-optical generation of 40 Gb/s single sideband signals using a fiber Bragg grating

In this work, we demonstrate a reliable all-optical technique for performing optical double sideband (ODSB) to single sideband (OSSB) format conversion of a 40 Gb/s non-return-to-zero signal. It is based on the optimization of a detuned optical filter, which was implemented on a fiber Bragg grating (FBG) with a complex apodization profile. An OSSB signal with negligible distortion was obtained, as the FBG presented a nearly ideal frequency response. Higher tolerance to chromatic dispersion enabled by the OSSB signal in comparison to the ODSB signal was demonstrated on both simulation and experimental results.     

Sideband manipulation of population inversion in a three-level Λ atomic system

Sideband manipulation of population inversion in a three-level A atomic configuration is investigated theoretically. Compared with the case of a nearly monochromatic field, a population inversion between an excited state and a ground state has been found in a wide sideband intensity range by increasing the difference in frequency between three components. Furthermore, the population inversion can be controlled by the sum of the relative phases of the sideband components of the trichromatic pump field with respective to the phase of the central component. Changing the sum phase from 0 to π, the population inversion between the excited state and the ground state can increase within nearly half of the sideband intensity range. At the same time, the sideband intensity range that corresponds to the system exhibiting inversion ρ00 〉 ρ11 also becomes wider evidently.     

Characterization of the IF Noise of a Submillimeter SIS Receiver

A fitting method is presented here for the accurate characterization of the IF noise contribution of a sub-millimeter SIS receiver. By fitting the mixer's IF output power response and junction's IV curve of an SIS mixer without LO pumping, we can obtain the IF noise contribution, the physical temperature of the isolator connected just behind the SIS mixer, the output mismatching of the mixer, and the total gain of the IF chain. Differing from a conventional method, which only uses the normal-state (linear) branch of the junction's IV curve, the method proposed here also includes the nonlinear portion around the gap voltage. The dynamic resistance in this portion is varied dramatically, providing us a good probe to characterize the output mismatching of the mixer, as well as other parameters.     

光的单边带传输的性能研究

对一种光单边带传输系统用MATLAB进行了仿真,结果表明：在完全消光条件下,10Gb/s单边带信号在常规单模光纤传输可达140 km, 而双边带仅为70 km;消光比对双边带传输和单边带传输的影响是不一样的. 双边带传输消光比为10 dB就够了, 单边带传输消光比要在20 dB以上,只有消光比大于20 dB时单边带传输相对于双边带传输的优越性才逐渐呈现出来.     

基于双通道马赫曾德尔调制器调制边带滤波的微波光子移相器

提出了一种基于双通道马赫曾德尔调制器(DPMZM)调制边带滤波的微波光子移相器。在双通道马赫曾德尔调制器的结构中,在一路马赫曾德尔干涉仪上实现抑制光载波的双边带调制输出,而在另一路马赫曾德尔的相位调节臂上通过调节偏置电压实现光载波信号的光学移相,两路光信号经过干涉合路后由光纤布拉格光栅(FBG)滤除其中一个一阶边带,最后输入到光电探测器(PD)进行光电转换得到移相的微波信号。实验结果表明,基于DPMZM调制边带滤波的微波光子移相器具有传输特性稳定、输出幅度波动小的优点。该结构还具有相移调节响应速度快、应用频带宽以及移相范围大于360°等特点。     

Resonant Brewster filters with absentee layers

A method for lowering the sideband levels associated with the spectral response of resonant waveguide-grating filters is presented. With a TM-polarized incident wave near the Brewster angle, the filter sidebands are suppressed by application of a half-wavelength absentee waveguide layer and an arbitrary-thickness grating layer. Adjusting the thickness of the grating layer permits control of the filter linewidth without appreciably affecting the sideband features. To verify the theoretical prediction, we fabricated and tested a double-layer waveguide-grating filter. It exhibited a peak efficiency of 82.4%, with sideband reflection levels below 0.6%, over a 95-nm spectral range.