Thermally controlled light filter

Journal of Applied Spectroscopy -     

Ultranarrow-bandwidth atomic filter with Raman light amplification

A Raman-amplified atomic filter is demonstrated experimentally. With a coupling light detuned from the D2 line of 85Rb, a weak signal light can be amplified by a factor of 55, and the bandwidth of the filter's transmission spectrum is narrowed to approximately 60 MHz. Moreover, the transmission wavelength is adjustable by changing the coupling-light frequency. Compared with a conventional dispersive atomic filter, this Raman-amplified atomic filter could be more efficient to suppress background noise in free-space quantum-key distribution or a laser-communication system.     

用空间滤波器改善光管式光学均匀器的性能

本文报道了一种用空间滤波改善光管式光学均匀性的技术，该技术使用空间滤波器滤除入射光束中光场突变部分，提高了光管式学均匀器的均匀性能。     

Active light noise filter by a differential operation

A method for an active light noise filter is proposed by using two identical light receivers. They work as a differential electrometer by a common mode connection. Therefore, only an output of a laser light incident upon one receiver can be obtained as a signal. It was found from the experiment that the light noise was reduced to about 0.6% in the usual light room and further the signal to noise ratio was improved up to 30 times at least as compared to a usual light shielding method. The method can then be effectively used under a well-lighted room such as a factory without noise light shielding cover.     

Optical properties of light filter designed on absorbing axicon

The optical properties of a light filter designed based on an absorbing axicon are studied. It is shown that if axes of the filter and a radially symmetric incident beam coincide, then the light transmission through the filter is minimal. This phenomenon can be used to find the beam center, radius and divergence, as well as to form properly collimated Gaussian beams. The filter allows the apodization and continuously tuning of the laser radiation intensity.     

Gram-Charlier matched filter for Shack-Hartmann sensing at low light levels

A study has been made of a Gram-Charlier matched filter for Shack-Hartmann sensing of wave-front slopes. The method is based on modeling the point-spread function by an expansion in terms of Gauss-Hermite polynomials. We present results for several subapertureycoherence area sizes both with and without CCD read noise. A more accurate estimation of the local slopes can be achieved at low light levels in this way than with the standard first-moment estimator.     

Wavelength tunable light filter. Choice of rotational axis position

The wavelength selected by a light filter is tuned by rotating the filter. The optimal positions are found for the rotational axis of a light filter used in different applications and meeting practical requirements. V. D. Kuznetsov Siberian Physicotechnical Institute at the State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 62–67, September, 1997.     

Mode analysis with a spatial light modulator as a correlation filter

A procedure for the real-time analysis of laser modes using a phase-only spatial light modulator is outlined. The procedure involves encoding into digital holograms by complex amplitude modulation a set of orthonormal basis functions into which the initial field is decomposed. This approach allows any function to be encoded and refreshed in real time (60 Hz). We implement a decomposition of guided modes propagating in optical fibers and show that we can successfully reconstruct the observed field with very high fidelity.     

Reflecting radial-shear interferometer

The use of a thick lens as a radial-shear interferometer is described. The two interfering beams are reflected from the two surfaces of the lens.     

Continuously tunable photonic microwave filter based on a spatial light modulator

An optical microwave filter architecture which can be continuously tuned is proposed and demonstrated. The architecture is based on a nematic liquid crystal spatial light modulator in parallel configuration and has the potential to control a large number of taps. Proof-of concept experimental results are provided.     

High-speed phosphorescent white LED visible light communications without utilizing a blue filter

We experimentally demonstrate a high-speed phosphorescent white light emitting diode(LED) visible light communication(VLC) system without utilizing an optical blue filter. Here, the white light response is equalized by using the proposed analog equalizers. The 3 d B bandwidth of the VLC link could be extended from 3 to132 MHz, which allows 330 Mbit/s non-return-to-zero on–off keying(NRZ-OOK) data transmission with a bit error ratio(BER) of 7.2 × 10-10 and 672 Mbit/s 64-quadrature amplitude modulation(64-QAM) data transmission with a BER of 3.2 × 10-3. These resultant BERs are less than the forward error correction(FEC) limit of3.8 × 10-3. The VLC link distance is 1 m using a single 1 W LED. The transmitter and receiver modules are integrated to a compact size. Furthermore, the relationships between the signal performance and illumination level or optical power are investigated and analyzed.     

Reflecting diffraction radiation oscillator

In this paper, linear theory and 3 dimension numerical calculations (R.DRO) are reported, the operation complex frequency equation is given. The test is carried out on a dynamical model, theoretical and test results of R.DRO have been analysed.     

Reflecting polarizing beam splitter

We propose and experimentally demonstrate the use of metal-covered lamellar relief gratings as a polarizing beam splitter operating at a single wavelength near Littrow incidence. We report the characteristics of a grating produced by holography and reactive ion etching that was calculated for operation as beam splitter at lambda = 633 nm (for a He-Ne laser).     

合肥光源横向束流反馈系统中矢量运算单元和光纤陷波滤波器的研制

合肥光源横向束流反馈系统已经建成,着重介绍了系统中矢量运算单元和光纤陷波滤波器的研制。矢量运算单元中使用混频器控制信号的衰减,调节控制电压的大小以控制反馈信号的相位;光纤陷波滤波器创新性地提出用光纤延时制作陷波滤波器,很好地滤除了信号中的回旋频率分量,节省了反馈功率。     

数字图像技术的数字滤光方法在图像测温中的应用

针对在比色测温法中由CCD光谱响应带宽引起的误差,提出了数字滤光的误差校正方法。该方法利用数字图像技术将光谱曲线离散化,采用离散化数据模型展开比色测温计算,在540±10nm绿光段和640±10nm红光段分别加入数字滤光算法,测温误差与外光路搭载滤光片效果接近。该方法简单实用,精度较高,在无外置滤光光路情况下实现了彩色CCD摄像设备的辐射测温,可为图像测温产品的便携性和适用化带来便利。     

合肥光源横向束流反馈系统中矢量运算单元和光纤陷波滤波器的研制

 合肥光源横向束流反馈系统已经建成,着重介绍了系统中矢量运算单元和光纤陷波滤波器的研制。矢量运算单元中使用混频器控制信号的衰减,调节控制电压的大小以控制反馈信号的相位;光纤陷波滤波器创新性地提出用光纤延时制作陷波滤波器,很好地滤除了信号中的回旋频率分量,节省了反馈功率。     

Wavelength-division multiplexing isolation fiber filter and light source using cascaded long-period fiber gratings

The author has successfully demonstrated a novel all-fiber wavelength-division multiplexing (WDM) isolation filter with more than 20 equally spaced loss peaks within a 60-nm band and a WDM light source with an output of 21 equally spaced wavelengths within 30% amplitude variation.