Various kinds of photo-detectors based on different materials have been successfully developed to expand the horizon of human eye. Spectral responsivity is the most important technical parameter for photo-detectors, which can mirror the converting ability of optical signal to electric current. Its measurement accuracy is critical for the development and research of photo-detecting field. In this paper, we will introduce the facility for photo-detector’s spectral responsivity calibration in the wavelength range of 300 nm to 1000 nm, built in National Institute of Metrology (NIM), China. Measurement uncertainty is analyzed at the wavelength 500 nm as an example. By adopting comparison method, choosing reference detectors with known standard value and traceable to SI units through upper level standards, we demonstrated a reliable measurement procedure for absolute spectral responsivity of photo-detectors.
Cryogenic radiometer is the most accurate measurement setup for optical power measurement, underpinning the radiometry and photometry standards in many countries around the world. Typically cryogenic radiometers are designed for laser injection, and the measurement uncertainty at the laser wavelengths can reach 10-4. The National Institute of Metrology China has used the laser cryogenic radiometer to realize the absolute spectral responsivity of the detectors. In order to achieve spectral responsivity measurement ability in a wider spectral range, we establish the new spectral type cryogenic radiometer system using a supercontinuum white light source and a double monochromator, covering spectral range of 400 nm - 1100 nm. Establishment of the new cryogenic radiometer will greatly enhance the entire optical radiation measurement capablities, such as radiation illuminance and luminance measurement. A series of experiments have been undertaken, including measurement of noise level, heating equivalence, wavelength calibration, power stabilization, detector characteristics measurement, and different light source spectral radiation power measurement. The measurement uncertainties are analyzed and presented.
The quantum efficiency of photon counters can be measured with standard uncertainty below 1% level using correlated photon pairs generated through spontaneous parametric down-conversion process. Normally a laser in UV, blue or green wavelength range with sufficient photon energy is applied to produce energy and momentum conserved photon pairs in two channels with desired wavelengths for calibration. One channel is used as the heralding trigger, and the other is used for the calibration of the detector under test. A superconducting nanowire single photon detector with advantages such as high photon counting speed (<20 MHz), low dark count rate (<50 counts per second), and wideband responsivity (UV to near infrared) is used as the trigger detector, enabling correlated photons calibration capabilities into shortwave visible range. For a 355nm single longitudinal mode pump laser, when a superconducting nanowire single photon detector is used as the trigger detector at 1064nm and 1560nm in the near infrared range, the photon counting efficiency calibration capabilities can be realized at 532nm and 460nm. The quantum efficiency measurement on photon counters such as photomultiplier tubes and avalanche photodiodes can be then further extended in a wide wavelength range (e.g. 400-1000nm) using a flat spectral photon flux source to meet the calibration demands in cutting edge low light applications such as time resolved fluorescence and nonlinear optical spectroscopy, super resolution microscopy, deep space observation, and so on.
Optical fiber power is an important physical quantity for optical fiber communication measurement. Currently, the absolute optical fiber power is traceable to absolute radiometer, such as electrically calibrated radiometer, and cryogenic radiometer. For optical fiber power transfer, the primary standard of NIM is the cryogenic radiometer that has an uncertainty of 2 parts in 104. Because most cryogenic radiometers are designed to be used with collimated beams rather than divergent beams from an optical fiber; therefore transfer standards should be well designed for optical power measurement using the beam geometry correction.
We designed a trap detector using for optical fiber power transfer. One can omit the beam geometry correction from an optical fiber using his design. We present a fiber power measurement using a planar detector compared with this trap detector, which are traceable to the primary standard (cryogenic radiometer). The difference between the comparison shows that the trap detector is suitable for absolute fiber power measurement, meanwhile optical fiber power transfer using planar detectors should be corrected when transferred from cryogenic radiometer.
Electrooptic sampling has been shown to be a very powerful technique for making time-domain measurements of fast electronic devices and circuits, such as oscilloscope. In this paper, we review the principles of electrooptic sampling technique for electronic waveform probing with applications to characterizing 100GHz photodetector pulse response.
In an imaging system based on a coherent source of moderate power density, images can be blurred when a biased photorefractive crystal is applied at the focal point of the imaging lens. In the frequency domain of the original images,
the intensity patterns are diffracted through the photorefractive crystal with varied bias voltage. The high intensity region,
which is usually the center or low frequency region of the intensity patterns, is more readily focused or defocused, resulting in blurred images in perception. Such blurred images could not be simply recovered by defocusing methods,
which can only indistinguishably focus or defocus the whole intensity patterns. However, the blurred images may be deblurred to certain extent for recovery if a second photorefractive crystal with bias voltage is employed at the focal point of a tandem imaging system. The mechanism of deblurring is similar to that of blurring: the blurred images are
transferred through the frequency domain again using an imaging lens, where the second biased photorefractive crystal
diffracts the intensity patterns to revert the sensitive region where previously gets focused or defocused. In this work,
theoretical analyses are presented in detail to explain the blurring-deblurring mechanism using two biased photorefractive crystals and compatible experimental results are obtained and illustrated. Considering the blurring and
deblurring function subgroups of the experiment setup can be potentially developed into encryption and decryption units
compatible with far field propagation, the technology presented herein may be promising to find applications in secure laser-based free-space communication systems.
A comparison of different transfer standard optical fiber power detectors is present. Traceable to cryogenic radiometer, these planar, focus-planar and trap detectors have different characteristics during the optical fiber power values transfer because of the different input angles or fiber connectors. For different types of fibers and fiber connectors, a new trap detector is capable for the optical fiber power measurement, which has very little sensitivity for a variety of input conditions. Comparison of fiber power measurement using a planar and a trap detector is present by employing a three-lens method. A good agreement between the two types of detectors shows the feasibility of fiber power transfer using planar detectors.
Degree of polarization (DOP) is an important physical quantity for describing the optical polarization effect and is widely applied in optical fiber communication, optical fiber gyro and the related technologies. Currently, the optical polarization degree tester for the purpose of communication uses mainly two kinds of measurement methods: Stokes vector method and extremum method. At present, there isn’t a standard to measure the accuracy and consistency of DOP parameter measurement by the devices listed above, affecting seriously the application of DOP parameter measurement in the fields of optical fiber gyro and optical fiber communication. So, it is urgent to table the accurate guarantees to trace the source of quantitative values of the DOP measuring devices and testers. In this paper, the polarization beam combination method is raised to research and manufacture the standard optical fiber light source device with the variable DOP, and an indicated error measurement has been conducted for a DOP meter. A kind of standard optical fiber light source device that uses a single light source to realize the variable DOP is put forward. It is used to provide the accurate and variable optical fiber polarization degree light with a scope of 0～100%. It is used to calibrate the DOP meters and widely applied in the field of national defense and optical communication fields. By using the standard optical power meter, DOP value by which the optical power meter calculates the optical signal can be measured, which will be used ultimately for calibration of the DOP meter. A measurement uncertainty of 0.5% is obtained using the polarization beam combination method.
In this paper, a kind of special optical fiber bonding high-temperature aging plan is raised. The armored optical fiber
technology is applied to guarantee the long-term stability of the optical properties of the standard instrument itself. The
temperature compensation encapsulation technology is adopted for optical fiber grating, that is, the wavelength will
remain constant under the standard atmosphere pressure and chamber temperature. It becomes the optical fiber grating
sensing wavelength standard instrument. The optical fiber grating standard instrument based upon this kind of new-type
structure is tested, and the result has its word that the temperature shift of this optical fiber grating standard instrument
after encapsulation is less than 0.5pm/℃. Coupled with the simple temperature control, the wavelength accuracy of the
optical fiber grating standard instrument will be controlled below ±1pm and its long-term stability will be smaller than
2pm/℃. Differ from F-P standard instrument, this optical fiber grating standard instrument is one without mechanical
device and is purely physical. So, it features more reliable performance and is applicable to mass production. The costs
of this kind of optical fiber grating standard instrument is under control and will see an important application in the
optical fiber grating sensing technology.