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Terahertz time-domain spectroscopy (THz-TDS) technology has developed rapidly in the past decades, and it has become an important method in the field of spectral analysis. Traditional THz-TDS can only analyze isotropic materials. But the need to add polarization analysis in THz-TDS is becoming more and more urgent. In this paper, a polarization THz-TDS system is established. The birefringence and polarization dependent loss parameters of YVO4, Iceland spar, MgF2, quartz in the terahertz band had been measured. Among them, the birefringence parameter of quartz, MgF2 and Iceland spar at 0.9 THz is in good agreement with the literature. The minimum polarization dependent loss of the four crystals between 0.2THz and 1.5THz are 3.03dB, 4.42dB, 4.4dB and 2.94dB, respectively.

Responsivity is one of the important technical parameters of the detector. With the development of ultraviolet detector technology, ultraviolet focal plane array devices have also been rapidly developed. Therefore, it is increasingly important to accurately measure the response of ultraviolet detectors. This paper analyzes the principle of UV focal plane array response measurement, uses the alternative method to measure the response of the UV focal plane array detection device, and establishes the UV focal plane array response measurement device. The results of uncertainty analysis show that the uncertainty of the UV focal plane array device response measurement system is about 4.2 %, can meet the measurement requirements.

Calibrating the absolute spectral responsivity is of great importance, because this guides the design and application of terahertz detectors. In this paper, we build a calibration system, and this system can be used to calibrate absolute spectral responsivity of terahertz detectors at a serial of frequencies such as 0.84, 1.63, 2.52, 4.25 THz et al. The key components of the system include a standard terahertz detector and a terahertz gas laser, and other components such as TPX lens and ultrasensitive voltmeter are also included. The calibration system was employed to calibrate a terahertz detector with the model of 12D-3S-VP produced by Gentec Inc., and the absolute spectral responsivity of 193.8 mV/W at 2.52 THz was obtained. The measurement uncertainty is analyzed to be 6.0%. This work not only offers method and system to terahertz detector calibration, but also contributes to high accuracy terahertz power measurement and terahertz device calibration.

Spectral response is one of the important technological parameters of the detector, along with the development of the ultraviolet detector technology, accurate measurement of UV detector spectral responsivity is becoming more and more important. This paper analyzes the ultraviolet focal plane array relative spectral responsivity measurement principle, using the substitution method of measuring ultraviolet focal plane array detector relative spectral responsivity, and established a calibration device for relative spectral response of UV focal plane array. The relative spectral response of UV focal plane array device was obtained,can be seen from the curves, UV focal plane array device from 250 nm to 290 nm spectral response range, the peak response near 270 nm, Show that the array sun-blind characteristic of a device. The uncertainty of analysis results showed that UV focal plane array device relative spectral response measurement uncertainty of calibration device is about 3.6%, can meet the demand of high precision measurement.

Terahertz technology is getting fast development in scientific research and the characteristics of terahertz beam is of great importance when using a terahertz laser. In this paper we scan the THz beam along its diameter by a slit and a circular aperture to measure the THz beam’s power distribution and thus get its spot’s size. The results show that the beam spot of the THz source we employed is satisfied with Gaussian distribution. The value of the peak power would affect the determination of the spot boundary, the influence of environmental noise will increases when the the peak power become weak and the measured spot diameter will be too large ultimately.

The wide spectrum of grating monochromator output wavelength accuracy is one of the main parameters of the monochromator, At present the calibration of monochromator output wavelength of most of the mercury lamp, to complete the calibration of the monochromator output wavelength in the visible range, but is unable to satisfy the calibration in the infrared wavelength. Aiming at the need for calibration, and based on the principle of grating diffraction, puts forword a method of using laser diffuse reflection method for measuring the wide spectrum of grating monochromator output wavelength accuracy. Select 632.8nm, 1550nm, 3.39µm three laser as the light source for calibration of grating monochromator, each laser measurement of three order diffraction. And the extension of the method of measurement uncertainty was evaluated and analysis, expanded measurement uncertainty of the method was 0.5%. Finally selects grating monochromator, the expanded uncertainty of measurement is verified, show that the measurement method is feasible, can meet the demand of high precision grating monochromator calibration.

Modulation transfer function (MTF) is one of the most important parameters of infrared focal plane array (IRFPA). A double-knife edge scanning method is proposed for MTF measurement of IRFPA. In this method, a double-knife edge was used as a target, and the IRFPA under test was positioned in the focal plane of the imaging optical system by a 3-axis translation stage. With an IRFPA data acquisition system, the image of the double-knife edge was restored. By scanning in the direction orthogonal to the double-knife edge image, edge spread function (ESF) curve of each pixel swept across the knife-edge image was obtained. MTF could be calculated from the subsequent fitting, differential and Fourier transformation procedures. With double-knife edge scanning, two ESF curves of double-knife edge were obtained simultaneously, and symmetry of the two ESF curves could be used to evaluate the verticality between photosensitive surface of IRFPA and optical axis of the double-knife edge imaging system. In addition, this method can be used to judge the existing of interference from outside such as vibration, stray light and electrical noise. A measurement facility for IRFPA’s MTF based on double-knife edge scanning method was also established in this study. The facility is composed of double-knife edge imaging optical system, 3-axis translation stage and data acquisition system, et al. As the kernel of the facility, the double-knife edge imaging optical system mainly comprises two symmetrical parabolic mirrors coating with reflective material, and the magnification of the optical system is 1 with an operation wavelength range of (1∼14) μm.

The method of knife-edge scanning is always adopted in testing the MTF of infrared focal plane array (IRFPA), and accurate focusing is one of the most important preconditions in the measurement procedure, because the measurement accuracy of MTF is ensured only when IRFPA is placed in the focal plane of the knife-edge imaging optical system. In this paper, a focusing method based on the area value under normalized MTF curve is proposed. Firstly, we analyzed MTF calculation model, which contained derivation of edge spread function (ESF) and then Fourier transformation. In this way, the issue of larger area under normalized MTF curve meant better focusing degree of the measurement system was proved. Next, the quasi-focal plane position of knife-edge optical system was determined according to the output voltage values of pixels of IRFPA. Then a series of MTF curves were measured when IRFPA was placed at different positions located in the optical axis beside the determined quasi-focal plane at an increment of 60 μm. Subsequently, the area under each normalized MTF curve was calculated, and the result showed the area values presented a perfect Lorentzian distribution against the positions of IRFPA. It was concluded the peak position of the fitted Lorentzian curve corresponded to the position of focal plane of knife-edge optical system. With this method, the focal plane position of knife-edge optical system was determined. The method presented here can be used to focus the MTF testing system with a high accuracy, which is good for the following MTF measurement.