Performance Of Phase Modulation Research Articles

A beam-steering antenna with low deflecting-loss enabled by a miniaturized flexible lens

A miniaturized flexible lens is proposed for beam control of broadband antenna with low deflection loss. Different from traditional approaches to phase modulation, the three-segment principle presented in this article significantly lowers the maximum necessary phase difference generated by modulated waves, thus reducing the height of the lens and antenna profile. The phase modulation performance of the lens is reconfigured by adjusting the layout of the phase modulation units PMUs according to distribution requirements. Then, a Vivaldi antenna utilizing the miniaturized lens is designed, fabricated, and tested to demonstrate the system’s beam deflecting characteristics. The experimental results demonstrate the capability of the antenna to cover a deflecting range wider than [−20°, 19°] with deflecting loss below 1.4 dB throughout the entire 8–10 GHz working band. Over the operating band, the deflecting gain is greater than 8.7 dBi.

Broadband high-efficiency near-infrared graphene phase modulators enabled by metal–nanoribbon integrated hybrid plasmonic waveguides

Abstract The phase modulator is a key component in optical communications for its phase modulation functions. In this paper, we numerically demonstrate a variety of ultra-compact high-efficiency graphene phase modulators (GPMs) based on metal–nanoribbon integrated hybrid plasmonic waveguides in the near-infrared region. Benefiting from the good in-plane mode polarization matching and strong hybrid surface plasmon polariton and graphene interaction, the 20 μm-length GPM can achieve excellent phase modulation performance with a good phase and amplitude decoupling effect, a low insertion loss around 0.3 dB/μm, a high modulation efficiency with V π L π of 118.67 V μm at 1.55 μm, which is 1–3 orders improvement compared to the state-of-the-art graphene modulators. Furthermore, it has a wide modulation bandwidth of 67.96 GHz, a low energy consumption of 157.49 fJ/bit, and a wide operating wavelength ranging from 1.3 to 1.8 μm. By reducing the overlap width of the graphene–Al2O3–graphene capacitor, the modulation bandwidth and energy consumption of the modulator can be further improved to 370.36 GHz and 30.22 fJ/bit, respectively. These compact and energy-efficient GPMs may hold a key to various high-speed telecommunications, interconnects, and other graphene-based integrated photonics applications.

A review of terahertz phase modulation from free space to guided wave integrated devices

Abstract In the past ten years, terahertz technology has developed rapidly in wireless communications, spectroscopy, and imaging. Various functional devices have been developed, such as filters, absorbers, polarizers, mixers, and modulators. Among these, the terahertz phase modulation is a current research hotspot. It is the core technology to realize flexible control of the terahertz wavefront, beam scanning, focusing deflection. It is indispensable in terahertz wireless communication, high-resolution imaging, and radar systems. This review summarizes the research progress of terahertz phase modulators from the two major types: free space and guided wave integration. Among these, the free space terahertz phase modulator is realized by combining the tunable materials and artificial metasurfaces. Based on different types of tunable materials, the terahertz free space phase modulator combining the semiconductor, liquid crystal, phase change materials, graphene, and other two-dimensional materials are introduced, and the influence of different materials on the phase modulation performance is discussed and analyzed. The monolithic integration and waveguide embedding methods are introduced separately, and the characteristics of different forms of terahertz-guided wave phase modulation are also discussed. Finally, the development trends of terahertz phase modulators, possible new methods, and future application requirements are discussed.

Application problems of liquid crystal phase modulators to high power lasers

The liquid crystal phase modulators (LCPMs) have applications and prospects in fusion ignition, laser processing, optoelectronic countermeasure, laser radar, laser communication, laser protection and so on. However, owing to the limited laser damage resistance of the materials constituting the LCPMs as well as insufficient system research on the laser damage and the phase modulation performance degradation of LCPMs induced by high power lasers, the laser handling power of LCPMs cannot satisfy the requirements of high power laser developments. To provide guidance for optimizing the fabrication process of LCPMs with high laser handling power, we reviewed the laser damage and the phase modulation performance degradation characteristics of LCPMs irradiated by high-peak-power lasers and high-average-power-lasers and then summarized the methods to improve the laser handling power of LCPMs.

Performance comparison of analogue inter‐satellite microwave photonics link using intensity modulation with direct detection and phase modulation with interferometric detection

The performance of optical inter-satellite communications using microwave photonics technologies employing intensity modulation with direct detection (IMDD) and phase modulation (PM) with interferometric detection are investigated and demonstrated with a numerical example. The theoretical model considering the saturated gain and amplifier spontaneous emission noise of optical booster amplifier and optical preamplifier is constructed for both architectures. Furthermore, the authors compare the performance of PM with interferometric detection to optimum biased IMDD in terms of radio frequency (RF) gain, RF noise figure and compression dynamic range (CDR). The numerical results show that the PM with interferometric detection can achieve better RF gain, RF noise figure and CDR than the optimum biased IMDD link as the laser output power is lower than 14.34, 12.45 and 4.2 dBm, respectively.

Study of oblique incidence characterization of parallel aligned liquid crystal on silicon

The phase-only liquid crystal on silicon (LCOS) spatial light modulator has been used as a wavefront generator and reconstruction device for display applications due to its phase-only modulating property of incident light. In order to achieve the best reconstructed phase modulated wavefront, the properties of LCOS have to be fully known. The intensity of reflected light from LCOS decreases under normal incidence by going through a beam splitter. In order to improve the intensity of the reflected light beam, the oblique incidence is preferred during many applications. The oblique incidence characterization of a parallel aligned LCOS is investigated at a working wavelength of 532 nm on the basis of double-hole interferometric method. Through experiments, the phase modulation characterization of LCOS under the oblique incidence is obtained. In addition, an image postprocessing method is proposed to overcome the effect of flicker and coherent noise by simplifying the computation and increasing the measurement accuracy. The comparison of experimental results for different incident angles indicates that it plays an important role in the performance of phase modulation of LCOS, where the phase modulation decreases with the increasing angle of incidence.

Performance of Phase Modulation in WDM-PON Transmission System

AbstractThe modulation and demodulation methods of the optical Differential Quadrature Phase Shift Keying (DQPSK), Optical Differential Phase Shift Keying (DPSK) and the different modulation formats including nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero (CS-RZ) are introduced, studying the ability of anti-dispersion for different optical signals in the 40 Gb/s high speed transmission system. The system is simulated in optical fiber by way of dispersion compensation. And then analyzed the compensation effect of the different dispersion compensation method for different phase modulation formats. It is shown that the ability of anti-dispersion and anti-PMD is better in the CS-RZ-DQPSK modulation format, and this format has the smallest eye-opening penalty (EOP) with a wider range of power into the optical fiber.

Evaluation of phase-only liquid crystal spatial light modulator for phase modulation performance using a Twyman–Green interferometer

In order to evaluate the phase modulation performance of a 256 × 256 pixel reflecting liquid crystal spatial light modulator purchased from the US Boulder Nonlinear Systems, we identify the linear range of phase shift and evaluate the spatial nonuniformity of the modulator by measuring both phase and intensity with a Twyman–Green interferometer. Experimental results show that the 50–210 grey scales linear ranges of the phase shift established by phase and intensity measurements are in good agreement with each other, which proves that more accurate phase modulation can be achieved. The inherent backplane curvature of the modulator is less than λ/3 and the root-mean-square value of the phase nonuniformity across the modulator aperture is less than λ/10, so the backplane curvature of the modulator is the main contributor to phase distortion due to the modulator. Analysing the deviation of the root-mean-square value of the phase nonuniformity indicates that the stability of the modulator decreases with increasing grey scales. It is therefore concluded that the modulator calibrated using a single interferometer can be used for beam steering, wave-front correction and transformation.

Frequency and phase modulation performance of an injection-locked CW magnetron

It is demonstrated that the output of a 2.45-GHz magnetron operated as a current-controlled oscillator through its pushing characteristic can lock to injection signals in times of the order of 100-500 ns depending on injection power, magnetron heater power, load impedance, and frequency offset of the injection frequency from the natural frequency of the magnetron. Accordingly, the magnetron can follow frequency and phase modulations of the injection signal, behaving as a narrow-band amplifier. The transmission of phase-shift-keyed data at 2 Mb/s has been achieved. Measurements of the frequency response and anode current after a switch of phase as a function of average anode current and heater power give new insight into the locking mechanisms and the noise characteristics of magnetrons

313 液晶SLMを用いたレーザトラッピングに関する基礎研究(OS6 マイクロ加工(1))

The purpose of this study to accomplish three-dimensional trapping of micro objects by a YAG laser with the Liquid Crystal Spatial Light Modulator (LCSLM). This paper describes a prototype experimental system. The experimental result shows that performance of phase modulation decreases with the increases of temperature of LCSLM. For this reason, the cooling system is necessary for LCSLM. The experimental result using cooling system shows a constant performance of phase modulation for a LCSLM. Using the cooled LCSLM, we have carried out the two-dimensional trapping of a particle. Using YAG laser a global trapping system has been developed by cooled LCSLM.

Dynamic range of coherent analog fiber-optic links

We investigate the performance of coherent analog optical links employing amplitude modulation (AM), phase modulation (PM), and frequency modulation (FM). The performance of these coherent links is compared to that of AM direct-detection (DD) links. The signal-to-noise ratios, nonlinearities, and-spurious-free dynamic ranges (SFDR's) of the foregoing links are evaluated. We calculate the SFDR for links using DFB and Nd:YAG lasers with typical linewidths of 10 MHz and 5 kHz, respectively. The performance of PM and FM links is dominated by phase noise above a critical value of received optical power. For a linewidth of 10 MHz, and SFDR's of PM and FM links are 30 and 31 dB, respectively, for a received optical power above -27 dBm in a 1 GHz bandwidth. For a linewidth of 5 kHz, the corresponding SFDR's above a received power level of 0 dBm are 51 and 53 dB. The performance of DD and AM links is dominated by RIN above a critical value of received optical power. For a RIN level of -155 dB/Hz, the SFDR's of DD and AM links are 49 and 47 dB, respectively, for a received optical power of 10 dBm in a 1 GHz bandwidth. The SFDR's of the DD and coherent links used for transmission of subcarrier-multiplexed (SCM) signals are also derived. We evaluate target laser parameters needed by a number of different applications. For AM video and antenna remoting applications, linewidths of >

Integrated optic devices based on nonlinear optical polymers

An examination is made of the state of the art of nonlinear optical polymeric materials in view of their potential advantages. It is shown that these organic materials have many attractive features compared to LiNbO/sub 3/ and III-V semiconductors with regard to their use in integrated optic circuits, especially since the level of integration is ever increasing. Considering more specifically electro-optic devices, a description is given of some of the theoretical background and basic properties. These polymers have already demonstrated a very high and extremely fast electro-optic effect compared to LiNbO/sub 3/. It is also shown how low-loss waveguides can be fabricated by using easy techniques such as direct UV bleaching. The performance of phase modulators, Mach-Zehnder interferometers, and 2*2 space switches built with such polymers is already very promising.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photoinduced conversion of radiation polarization in integrated optics components based on LiNbO/sub 3/

Two photoinduced effects in LiNbO/sub 3/ optical waveguides (unidirectional waveguide mode conversion from ordinary to extraordinary polarization and radiation coupling out of waveguides with polarization plane rotation) are discussed. The circular photovoltaic tensor component in LiNbO/sub 3/ is determined experimentally, and a photovoltaic mechanism to explain photoinduced radiation coupling out of waveguides is proposed. The impact of the effects discovered on the performance of phase modulators is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Carrier Transmission of Binary Data in a Restricted Band

The spectra of digital frequency modulation (FM) signals have been observed to be narrow compared with the spectra of digital baseband signals or the corresponding amplitude modulation (AM) and phase modulation (PM) signals. This suggests a high efficiency of transmission in terms of occupied bandwidth for binary FM. Here the desirability of digital FM systems is investigated further with an examination of the probability of bit error. The FM receiver considered consists of a predetection filter, a limiter-discriminator, and a postdetection filter. New results are presented on the effect of predetection bandwidth restriction on the error performance of binary FM systems for various frequency deviations. Theoretical results have been obtained by a Fourier analysis of the distorted FM signals and by Rice's click analysis of FM noise. The data presented permits an optimum selection of system parameters such as frequency deviation ratio and predetection filter bandwidth. It is found that in narrow-band operation a peak-to-peak frequency deviation of about 0.7 times the bit rate and a bandpass filter bandwidth of about 1.0 times the bit rate yield a minimum probability of error. Experimental measurements have been made and there is, in general, good agreement with the theory. A comparison of the error performance of noncoherent binary FM, coherent AM, and coherent PM in a restricted band is made. Narrow-band noncoherent FM proves superior to AM in any bandwidth. In narrow-band operation, the noncoherent FM gives a somewhat better error performance than the coherent PM. For example, for an error rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> and a bandpass filter bandwidth of one times the bit rate, the performance of a noncoherent FM system is 0.7 dB better than that of a coherent PM system.