1.Basic concept of TRAL  test system  

 TRAL test station is a modular universal test station designed to measure parameters of discrete optical detectors  sensitive in a wide spectral range from 280 nm to over 15 000 nm (UV detectors, visible detectors/NIR detectors, SWIR  detectors, MWIR detectors, LWIR detectors or broadband detectors). All typical types of optical detectors can be tested: photonic detectors: photovoltaic/photoresistive, cooled/non-coooled, Si, InGaAs, InSb, HgCdTe), thermal detectors, pyroelectric detectors. 

Typical test capabilities of TRAL station

1. Relative spectral sensitivity function
2. Noise parameters (noise level, normalized detectivity, spectral detectivity)
3. Responsivity parameters (responsivity, linearity, dynamic)

The station is built from the following blocks:

1. Set of optical  sources (IR 314 source, IR 2300 sourceUV13, HTCB 1000-25D blackbody)
2. Set of M250 series monochromator (monochromators of different spectral range are available)
3. Controller of the M250 monochromator
4. OS 3 optical stage (option OS 3M motorized 2D station)
5. OM chopper
6. TDM-1 detection module
7. SAM signal analysis  (different options are available)
8. PC
9. SPEC computer program

 

Fig. 1. Block diagram of  TRAL  station

In general the TRAL station irradiates  the tested  detector  using variable wavelength radiation. In this way  and measures the response of the tested detector to the  incoming radiation. The principle of work of this station is following.  One of  high intensity polychromatic source of optical  radiation  irradiates the input slit of the M250 monochromator that is used as a variable wavelength selector. The output slit of the M250 monochromator  emits radiation of the wavelength controlled by the user.  The output analog signal from the tested detector  amplified and later converted to digital domain by SAM module and sent to PC. Because calibrated sources of known radiant intensity are used and additionally the recorded signals from tested detector can be compared to a signal from standard broadband TDM detection module therefore test software SPEC can calculate parameters of tested detector: relative spectral sensitivity function, noise parameters (noise level, normalized detectivity, spectral detectivity), responsivity parameters (responsivity, linearity, dynamic).

TRAL can be also used to measure emission spectrum of unknown optical sources.  Then this optical  source should be located at the monochromator input instead of standard sources. 

2. Versions of TRAL station    

TRAL  test station can be delivered at form of different versions of different configuration of different measurement capabilities and optimised for different spectral ranges. TRAL can be defined using a four digit code as shown in table below.   For example TRAL 3334 means a test station capable to measure  Spectral/noise/response parameters of SWIR photovoltaic detectors in  frequency range at least from DC to 2 GHZ.

 Tab. 1. Versions of TRAL test station   

Code	Test capabilities	Spectral range	Detector type	Frequency range
1	Spectral parameters	UV	Thermal	DC-100Hz
2	Noise/response parameters	VIS/NIR	Pyroelectric	DC-100kHz
3	Spectral/noise/response parameters	SWIR	Photovoltaic	DC-100MHz
4		MWIR	Photoresistor	DC-2GHz
5		LWIR	Thermal/ pyroelectric	To be determined by customer
6		UV/VIS/NIR	Photovoltaic/ photoresistor
7		IR (700-15000nm)	All types
8		Broadband (280-15 000nm)

 

In order to learn more about the TRAL  test system please contact us.

 

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