Abstract
We have developed an up-conversion spectrometer for signals at single photon levels near the infrared region based on a tunable up-conversion detector that uses a periodically poled lithium niobate waveguide as the conversion medium. We also experimentally studied its characteristics including sensitivity, dark count rate, spectral scan speed, signal transfer function of the waveguide, and polarization sensitivity. The overall single photon detection efficiency of the up-conversion spectrometer is about 32%. With its ultra high sensitivity the spectrometer can measure spectra for signals at a level as low as -126 dBm. We have demonstrated the spectrometers high sensitivity by measuring the spectrum of a greatly attenuated multimode emission from a laser diode at the 1310 nm band.
Highlights
An infrared (IR) spectrometer for weak light at single-photon level is a very important tool in many areas of research in physics, chemistry and biology, and may have applications in forensics
Similar to the up-conversion detector that we developed previously [4, 5], the spectrometer uses a 5-cm periodically poled lithium niobate (PPLN) waveguide as a nonlinear medium to implement the sum frequency generation (SFG)
The output light of PPLN waveguide, including 710 nm (SFG), 1550 nm pump and its second harmonic generation (SHG) 775 nm, are separated by two dispersive prisms and the 710-nm photons are detected by a silicon avalanche photodiodes (Si-APDs) (PerkinElmer: SPCM-AQR-14)
Summary
An infrared (IR) spectrometer for weak light at single-photon level is a very important tool in many areas of research in physics, chemistry and biology, and may have applications in forensics. For UV, visible and wavelengths shorter than 1 μm, there are many choices for detectors with excellent performance In this region the detection efficiency of silicon- based detectors (or arrays) is very high while their intrinsic noise is very low. Those photons, whose momentum and energy conservations requirements are satisfied with the phase-matching condition in the waveguide, can be converted and detected Based on this principle, an up-conversion spectrometer can be constructed when a tunable pump source is used [6,7,8]. We have developed an up-conversion spectrometer, which uses a tunable pump source around 1550 nm to convert signal photons at the 1310-nm band into the 710 nm in a PPLN waveguide. We will report on the up-conversion spectrometer and experimentally study its performance, including its sensitivity, maximum input signal intensity, scan speed, waveguide transfer function response, and polarization sensitivity
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