共查询到20条相似文献,搜索用时 31 毫秒
1.
Displacement measurements and position sensing have been playing an important role in many fields such as fabrication, biophysics, and autocontrol. Interferome- try, laser triangulation, optical fiber sensing and moiré technique are common optical measuring methods[1-3]. Among these methods, moiré technique holds the most interest due to its high accuracy, large range, low cost, and other advantages. When a long working distance is required, or when space is not at a premium, a moiré sys- t… 相似文献
2.
Pulse re-shaping by using a liquid crystal spatial light modulator and deflector for producing a specific waveform 总被引:2,自引:0,他引:2
A new shaping method for producing nanosecond pulses with specific shape is introduced. When a Gaussian laser pulse passes through an electro-optic deflector, it has been scanned as a line on the focal plane according to time precedence. Through controlling the intensity of transmitted light on each pixel of the liquid crystal spatial light modulator (LCSLM), various complicated pulses can be easily produced. Using this method, various specific shaped pulses with pulse duration varying from 750 ps to 5 ns are achieved. 相似文献
3.
Electro-optic material has several applications in optical communication, integrated optics and in data processing. The modulator is generally used for the purpose of amplitude and phase modulation of optical wave by the electrical message signal. Again the Vπ voltage of an electro-optic modulator is an important parameter for the modulator. For the application of the Vπ amount of electrical signal in the modulator the phase difference between two specific orthogonally polarized light waves changes from 0 to π. Thus the increase of Vπ relates with the increase of electrical power requirement for modulation. Here in this paper the authors propose a new and novel concept for reduction of Vπ voltage for the modulator. To reduce the value of the Vπ voltage the multi passing technique of the beam through the modulator is used. If Vπ is reduced the power requirement as well as the modulation cost will be greatly reduced to achieve a faithful and a meaningful optical communication. This paper describes also the necessary optical systems required for the multi passing technique. 相似文献
4.
Silicon-on-insulator (SOI) technology offers tremendous potential for integration of optoelectronic functions on a silicon wafer. In this letter, a 1 x 1 multimode interference (MMI) Mach-Zender interferometer (MZI) thermo-optic modulator fabricated by wet-etching method is demonstrated. The modulator has an extinction ratio of -11.0 dB, extra loss of -4.9 dB and power consumption of 420 mW. The response time is less than 30μs. 相似文献
5.
In this Letter,a novel system for adaptively correcting the phase of a dynamic multimode beam is proposed.While using merely one spatial light modulator,the phase measurement of the first-order diffraction pattern and the correction of the zeroth diffraction order are simultaneously realized.The real-time experimental result is obtained at a control rate of 10 Hz.The power-in-the-bucket value is improved from 38.5%to 61.8%,even with fundamental mode content that is consistently below 30%.To the best of our knowledge,this is the first implementation of real-time adaptive correction of the entire multimode beam. 相似文献
6.
《中国光学快报(英文版)》2015,(6)
We propose and experimentally demonstrate an ultra-flat optical frequency comb(OFC) generator by a balanced driven dual parallel Mach–Zehnder modulator. Five- and seven-tone OFC with exactly equal intensity can be generated theoretically. Experimentally obtained five- and seven-tone OFC with flatness of 0.6 and 1.26 d B are demonstrated, respectively, which agrees well with the theoretical results. 相似文献
7.
Noise caused by a finite extinction ratio of the light modulator in?CW cavity ring-down spectroscopy
A model is presented for the effect of a finite extinction ratio of the light modulator used in continuous wave cavity ring-down
spectroscopy (CW-CRDS) experiments. We present a simple analytical expression for the minimum isolation required to prevent
a significant increase in the fluctuations of the cavity decay rate, which determine the sensitivity of the method. We also
present systematic measurements of the signal to noise in CW-CRDS as a function of the effective isolation of the light modulator,
and excellent agreement with the model is found. 相似文献
8.
The research on the interaction of the light and microwave and the swift development of fiber communication with high code velocity promotes the advancing of the waveguide modulator. In this paper, we presented a new simple method with very clear physical concept to calculate the highest modulated frequency of waveguide modulator, and we also do a comprehensive research on the characteristics of modulator, and deduce accurate formula and characteristic curves. These researches will be very important to the application of waveguide modulator. 相似文献
9.
By applying the microring resonator to the Mach-Zehnder (MZ) optical modulator and employing the super-linear phase change characteristic of the all-pass filter, the sublinear modulation curve of the conventional MZ modulator is highly linearized. With properly controlled power coupling between the microring and the arm of the MZ modulator, the third-order distortion can be suppressed. If the transmission coefficient is set between 0.25 and 0.42, the linearity range larger than 90% can be easily achieved. The maximum linearity range is even up to 99.5%. 相似文献
10.
This paper proposes a simple, compact, practical, less nonlinear, less decorrelation and multi-purpose phase modulator for one beam ESPI which can be used perform both phase shifting and fringe carriering techniques. Theory together with experimental demonstrations are presented. 相似文献
11.
A Brimont DJ Thomson FY Gardes JM Fedeli GT Reed J Martí P Sanchis 《Optics letters》2012,37(17):3504-3506
In this Letter, we demonstrate a highly efficient, compact, high-contrast and low-loss silicon slow wave modulator based on a traveling-wave Mach-Zehnder interferometer with two 500?μm long slow wave phase shifters. 40 Gb/s operation with 6.6?dB extinction ratio at quadrature and with an on-chip insertion loss of only 6?dB is shown. These results confirm the benefits of slow light as a means to enhance the performance of silicon modulators based on the plasma dispersion effect. 相似文献
12.
We propose a novel and simple scheme to achieve NRZ-to-RZ format conversion and simultaneous wavelength multicasting based on a single-stage dual-arm electro-optic Mach–Zehnder modulator (MZM) and a short single mode fiber (SMF). The format conversion and wavelength multicast process are achieved by chirp compensation under the condition of generation of optical flat frequency comb. 40 Gb/s NRZ-to-RZ conversion with one-to-five multiple-wavelength channel multicasting and transmission of the NRZ and the converted signals over 200 km dispersion-managed fiber-link are successfully demonstrated by numerical simulation. Research results show that 40 Gb/s 2 ps RZ signal with wavelength-preserving can be obtained after format conversion. The converted RZ signal presents good transmission performance and can easily be multiplexed to 160 Gb/s using optical time division multiplexing (OTDM) technology. All the multicast channels can be error free after 50 km transmission. Besides, the conversion operation can also greatly reduce the timing jitter of the degraded NRZ signal due to the retiming function of the proposed scheme. 相似文献
13.
This paper proposes a simple, compact, practical, less nonlinear, less decorrelation and multi-purpose phase modulator for one beam ESPI which can be used perform both phase shifting and fringe carriering techniques. Theory together with experimental demonstrations are presented. 相似文献
14.
15.
《Superlattices and Microstructures》1998,23(2):253-259
In this paper photoluminescence measurements at low temperature under different excitation powers were carried out on an InGaAs tensile strained (x = 0.3) quantum well with InGaAs barriers lattice matched (LM) to InP. Evidence of a type-II recombination was found between carriers confined in the tensile layer and in the LM layer. This study allows us to deduce an accurate determination of the conduction band offset in the In0.3Ga0.7As/In0.53Ga0.47As/InP system. Moreover, we include the previous type-II structure between InAlAs barriers in order to confine both electrons and holes. This structure has potential applications in electro-optical modulators. We simulate its optical modulation by solving the Schrödinger equation using the envelope function approximation and calculating the absorption spectrum taking into account excitonic effects. 相似文献
16.
Viktoriia E. Babicheva Radu Malureanu Andrei V. Lavrinenko 《Photonics and Nanostructures》2013,11(4):323-334
We propose a plasmonic waveguide with semiconductor gain material for optoelectronic integrated circuits. We analyze properties of a finite-thickness metal–semiconductor–metal (F-MSM) waveguide to be utilized as an ultra-compact and fast plasmonic modulator. The InP-based semiconductor core allows electrical control of signal propagation. By pumping the core we can vary the gain level and thus the transmittance of the whole system. The study of the device was made using both analytical approaches for planar two-dimensional case as well as numerical simulations for finite-width waveguides. We analyze the eigenmodes of the F-MSM waveguide, propagation constant, confinement factor, Purcell factor, absorption coefficient, and extinction ratio of the structure. We show that using thin metal layers instead of thick ones we can obtain higher extinction ratio of the device. 相似文献
17.
Viktoriia E. Babicheva Irina V. Kulkova Radu Malureanu Kresten Yvind Andrei V. Lavrinenko 《Photonics and Nanostructures》2012,10(4):389-399
We investigate plasmonic modulators with gain material to be implemented as ultra-compact and ultra-fast active nanodevices in photonic integrated circuits. We analyze metal–semiconductor–metal (MSM) waveguides with InGaAsP-based active material layers as ultra-compact plasmonic modulators. The modulation is performed by changing the gain of the core, that results in different transmittance through the waveguides. A MSM waveguide enables high field localization and therefore high modulation speed. Bulk semiconductor, quantum wells and quantum dots, arranged in either horizontal or vertical layout, are considered as the core of the MSM waveguide. Dependences on the waveguide core size and gain values of various active materials are studied. The designs consider also practical aspects like n- and p-doped layers and barriers in order to obtain close to reality results. The effective propagation constants in the MSM waveguides are calculated numerically. Their changes in the switching process are considered as a figure of merit. We show that a MSM waveguide with electrical current control of the gain incorporates compactness and deep modulation along with having a reasonable level of transmittance. 相似文献
18.
In this Letter, we reported the preliminary results of an integrating periodically capacitive-loaded traveling wave electrode(CL-TWE) Mach–Zehnder modulator(MZM) based on InP-based multiple quantum well(MQW)optical waveguides. The device configuration mainly includes an optical Mach–Zehnder interferometer, a direct current electrode, two phase electrodes, and a CL-TWE consisting of a U electrode and an I electrode. The modulator was fabricated on a 3 in. InP epitaxial wafer by standard photolithography, inductively coupled plasma dry etching, wet etching, electroplating, etc. Measurement results show that the MZM exhibits a3 dB electro-optic bandwidth of about 31 GHz, a V_π of 3 V, and an extinction ratio of about 20 dB. 相似文献
19.
Fei Fan Wei Li Wen-Hao Gu Xiang-Hui Wang Sheng-Jiang Chang 《Photonics and Nanostructures》2013,11(1):48-54
The transmission and tuning properties of a cross-shaped plasmonic crystal based on periodic metal–semiconductor–metal (MSM) structures have been investigated in the terahertz (THz) regime. According to the mode analysis, we find that the different resonance modes in the plasmonic crystal show the different changes when this device is actively controlled by the carrier injection of the MSM structures. The longitudinal modes disappear, while the horizontal mode moves to a higher frequency. The former leads to an intensity modulation at 0.5 THz and 1.1 THz when the groove depth h = 60 μm, and the later leads to a band blue-shift from 1.325 THz to 1.38 THz. These results will be applied to THz modulation and tunable filtering. 相似文献
20.
The PZT optical fiber phase modulator testing with varying amplitude modulation¥YANGYuanhong;MAJing;ZHANGWeixu(TabsibResearch... 相似文献