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FT光谱仪测量调制光和脉冲光的应用实例/APPLICATION NOTE: MODULATED & PULSED LIGHT S OURCES
日期：2024-04-25 02:52
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摘要：
FT光谱仪测量调制光和脉冲光的应用实例/APPLICATION NOTE: MODULATED & PULSED LIGHT S OURCES
This application note describes the use of ARCspectro FT -NIR and FT-MIR for measuring modulated (or
pulsed) light sources. It is shown that pulsed light sources with frequencies ranging from 10kHz to over
80Mhz can be measured with our systems.
I NTRODUCTION
The ARCspectro FT series are scanning Fourier-transform spectrometers. These instruments use a white -light interferometer to record an interferogram by scanning the position of one of the interferometer
mirrors. Nevertheless, time -varying light sources can be measured with the Arcspectro FT series , provided
that the frequency of the source lies outside the interfe rometer modulation frequenc y range. Typically, the
interfe rometer modulation frequencies are in the order of a few kHz. Furthermore, a digital filter is
implemented in the processing, which fil ters out any frequency component lying outside the 100 Hz - 10kHz
range (these are indicative values that might differ from one spectrometer type to another). Modulated or
pulsed light sources can be measured provided that their f requency (or repetition rate) lies above of the
higher interferometer modulation frequency (typically 10kHz) . Below are three measurement examples .
E XAMPLE 1 – P ULSED LED 1550NM
As a first example, a 2.5mW LED emitting broadly around 1. 55𝜇𝑚 was measured using a n ARCspectro FT -NIR equipped with a 0.9 -2.6 microns InGaAs detector. T he LED output was modulated at different
frequencies using a function generator .
Figure 1 shows 10 subsequent measured spectra of the LED modulated at 15 kHz . T his frequency is above
the interfe rometer modulation frequencies and internal digital fileter. T herefore, t he spectrum of th e LED is
measured normally.
This application note describes the use of ARCspectro FT -NIR and FT-MIR for measuring modulated (or
pulsed) light sources. It is shown that pulsed light sources with frequencies ranging from 10kHz to over
80Mhz can be measured with our systems.
I NTRODUCTION
The ARCspectro FT series are scanning Fourier-transform spectrometers. These instruments use a white -light interferometer to record an interferogram by scanning the position of one of the interferometer
mirrors. Nevertheless, time -varying light sources can be measured with the Arcspectro FT series , provided
that the frequency of the source lies outside the interfe rometer modulation frequenc y range. Typically, the
interfe rometer modulation frequencies are in the order of a few kHz. Furthermore, a digital filter is
implemented in the processing, which fil ters out any frequency component lying outside the 100 Hz - 10kHz
range (these are indicative values that might differ from one spectrometer type to another). Modulated or
pulsed light sources can be measured provided that their f requency (or repetition rate) lies above of the
higher interferometer modulation frequency (typically 10kHz) . Below are three measurement examples .
E XAMPLE 1 – P ULSED LED 1550NM
As a first example, a 2.5mW LED emitting broadly around 1. 55𝜇𝑚 was measured using a n ARCspectro FT -NIR equipped with a 0.9 -2.6 microns InGaAs detector. T he LED output was modulated at different
frequencies using a function generator .
Figure 1 shows 10 subsequent measured spectra of the LED modulated at 15 kHz . T his frequency is above
the interfe rometer modulation frequencies and internal digital fileter. T herefore, t he spectrum of th e LED is
measured normally.
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EXAMPLE 2 - 80MH Z B ROAD- BAND SUPERCONTINUUM SOURCE
A pulsed supercontinuum source similar to, but not identical to, a NKT Photonics SuperK Extreme EXW -12
system was measured on a Arcoptix FT -MIR 2.0-6.0.
This supercontinuum source delivers light in ca 500 ps pulses with 80 MHz covering a spectrum of 450-2400
nm with an average power of about 5W. The spectrum was mea sured on the Arcoptix FT -MIR 2-6.0 with a
diffusion lens before the FT -MIR to reduce the intensity of the 1mm collimated beam from the
supercontin uum source. T he laser power was varies from 20 to 100%. Results are shown on Figure 3 .
