Frequency response and applications of optical electric-field sensor at frequencies from 20 kHz to 180 GHz

This article describes the frequency response and the applications of the optical electric-field sensor consisting of a 1 mm1 mm1 mm CdTe crystal mounted on the tip of an optical fiber, which theoretically possesses the potential to cover the frequency band from below megahertz to terahertz. We utilize a capacitor, GTEM-Cell, and standard gain horn antennas for applying a free-space electric field to the optical sensor at frequencies from 20 kHz to 1 GHz, from 1 GHz to 18 GHz, and from 10 to 180 GHz, respectively. An electric-field measurement demonstrates its flat frequency response within a 6-dB range from 20 kHz to 50 GHz except for the resonance due to the piezo-electric effect at a frequency around 1 MHz. The sensitivity increases due to the resonance of the radio frequency wave propagating in the crystal at the frequencies higher than 50 GHz. These experimental results demonstrate that the optical electric-field sensor is a superior tool for the wide-band measurement which is impossible with conventional sensors such as a dipole, a loop, and a horn antenna. In transient electrostatic discharge measurements, electric-field mapping, and near-field antenna measurements, the optical electric-field sensor provide the useful information for the deterioration diagnosis and the lifetime prognosis of electric circuits and devices. These applications of the optical electric-field sensor are regarded as promising ways for sowing the seeds of evolution in electric-field measurements for antenna measurement, EMC, and EMI

Universal optical electric-field sensor covering frequencies from 10 to 100 GHz

This article describes an optical sensor that can accurately measure electric-field strength at frequencies ranging from 10 to 100 GHz. The optical sensor utilizes a 1 mm times 1 mm times 1 mm CdTe crystal mounted on the tip of an optical fiber, which theoretically possesses the potential to cover the frequency band from several megahertz to terahertz. A free-space electric-field measurement demonstrates its flat frequency response within a 6-dB range from 10 to 50 GHz. The sensitivity increases due to the resonance of the radio frequency wave propagating in the crystal at the frequencies higher than 50 GHz. The optical sensor can accurately measure the distribution of the electric field radiated from a horn antenna at 100 GHz

Latest trends in millimeter-wave imaging technology,”

Abstract-This paper overviews the latest trends of millimeterwave (MMW) imaging technologies, focusing mainly on applications of and technical parameter variations for security surveillance and nondestructive inspections (NDI). We introduce a smart NDI tool using active W-band imaging, which is capable of detecting hidden surface cracks in concrete structures

Generation of frequency-modulated sub-terahertz signal using microwave photonic technique

We present a photonic technique for generating a frequency-modulated sub-terahertz signal for non-destructive or noninvasive sensing and imaging applications. Large frequency deviation was achieved by using optical phase modulation and heterodyne photomixing with an uni-travelling photodetector. The operation principle is theoretically derived and explained. In addition, the generation of 350-GHz frequency-modulated sub-terahertz signal with 6.7-GHz frequency deviation is experimentally demonstrated, and the possibility of frequencies up to 1 THz and wider frequency deviations is discussed. (C) 2010 Optical Society of America1166sciescopu

Photonic generation of millimeter and terahertz waves and its applications

1

Microwave Photonic Noise Source from Microwave to Sub-Terahertz Wave Bands and Its Applications to Noise Characterizations

In this paper, we present a microwave photonic technique to produce a noise signal from the microwave to sub-terahertz region with an optical amplified spontaneous emission noise, optical filter, and photodetector. With this scheme, it is easy to control the noise level by simply controlling the input optical noise power. In addition, the output noise spectral density with this scheme can be accurately estimated from the well-known spectral shape of an optical filter. For the demonstration of this scheme as a noise source, noise figure measurements for commercial devices such as amplifiers and a mixer, were performed in the frequency range from 0.1-20 to 293-357 GHz and the results were compared to those with conventional techniques.111417sciescopu

A 325 GHz Quadrature Voltage Controlled Oscillator With Superharmonic-Coupling

We present a 325 GHz quadrature voltage controlled oscillator (QVCO) using 0.25 mu m InP HBT technology and superharmonic coupling of two differential Colpitts VCOs. The individual VCOs exhibit about -5-dBm single-ended output power and 10 GHz frequency tuning range. The quadrature oscillation is successfully demonstrated with dc power consumption of 92.4 mW and phase imbalance less than +/- 12 degrees at around 325 GHz.1178sciescopu

50-Gb/s Direct Conversion QPSK Modulator and Demodulator MMICs for Terahertz Communications at 300 GHz

We demonstrate direct quadrature modulator and demodulator monolithic microwave integrated circuits for future terahertz communications at 300 GHz based on the quadrature phase-shift keying (QPSK) modulation format. For the modulating and demodulating signal, we employed half-Gilbert cell mixers, which provide balanced signaling and moderate performance in conversion efficiency with a simple circuit configuration. In order to maintain the balance performance of the modulator and demodulator, passive baluns and couplers are implemented with thin-film microstrip lines, which exhibit less insertion loss than inverted microstrip lines (IMSLs), while the active mixers are based on IMSLs for short interconnections. The half-Gilbert-cell mixers have a wide enough operation bandwidth for high-throughput communications of more than 10% at 300 GHz. According to the static constellation of the modulator, imbalance is expected to be less than approximately +/- 0.6 dB angle 4 degrees. A nonchip back-to-back experiment was conducted at up to 60 Gb/s, and 50-Gb/s operation was verified with a low bit error rate on the order of 10(-8) or less. The results demonstrate that the QPSK modulation scheme can be applied to double the data rate at terahertz frequencies.115247sciescopu

Uni-Travelling-Carrier Photodiode Module Generating 300 GHz Power Greater Than 1 mW

In this letter, we demonstrate over 1 mW power generation at 300 GHz with a uni-travelling-carrier photodiode (UTC-PD) packaged in a WR-3 waveguide module. To increase the maximum power, two identical UTC-PDs were monolithically integrated along with a T-junction to combine the power from the two PDs. The UTC-PD module exhibited peak saturated output power of approximately 1.2 mW at 300 GHz with photocurrent of around 20 mA per PD and bias voltage of -3.9 V. In addition, 3 and 10 dB bandwidths were measured to be around 70 GHz or 23% and over 150 GHz or 50%, respectively.114245sciescopu