Method and apparatus for improved signal to noise ratio in Raman signal detection for MEMS based spectrometers
First Claim
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1. A method of Raman detection for a portable, integrated spectrometer instrument, the method comprising:
- directing Raman scattered photons by a sample to an avalanche photodiode (APD), said APD configured to generate an output signal responsive to the intensity of said Raman scattered photons incident thereon;
amplifying said output signal of said APD and passing said amplified output signal through a discriminator so as to reject at least one or more of amplifier noise and dark noise;
counting a number of discrete output pulses within a set operational range of said discriminator so as to determine a number of photons detected by said APD; and
passing said output signal of said APD through a preamplifier so as to shape an output current pulse from said APD to a NIM standard pulse.
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Abstract
A method of Raman detection for a portable, integrated spectrometer instrument includes directing Raman scattered photons by a sample to an avalanche photodiode (APD), the APD configured to generate an output signal responsive to the intensity of the Raman scattered photons incident thereon. The output signal of the APD is amplified and passed through a discriminator so as to reject at least one or more of amplifier noise and dark noise. A number of discrete output pulses within a set operational range of the discriminator is counted so as to determine a number of photons detected by the APD.
25 Citations
14 Claims
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1. A method of Raman detection for a portable, integrated spectrometer instrument, the method comprising:
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directing Raman scattered photons by a sample to an avalanche photodiode (APD), said APD configured to generate an output signal responsive to the intensity of said Raman scattered photons incident thereon; amplifying said output signal of said APD and passing said amplified output signal through a discriminator so as to reject at least one or more of amplifier noise and dark noise; counting a number of discrete output pulses within a set operational range of said discriminator so as to determine a number of photons detected by said APD; and passing said output signal of said APD through a preamplifier so as to shape an output current pulse from said APD to a NIM standard pulse. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for Raman detection within a portable, integrated spectrometer instrument, comprising:
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an avalanche photodiode (APD) integrated on a chip, said APD configured to receive Raman scattered photons by a sample and generate an output signal responsive to the intensity of said Raman scattered photons incident thereon, wherein said APD is biased in a sub-Geiger mode of operation; an amplifier integrated on said chip, said amplifier configured to amplify said output signal of said APD and pass said amplified output signal though a discriminator integrated on said chip, so as to reject at least one or more of amplifier noise and dark noise; and a digitizer integrated on said chip, configured to count a number of discrete output pulses within a set operational range of said discriminator so as to determine a number of photons detected by said APD. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method of Raman detection for a portable, integrated spectrometer instrument, the method comprising:
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directing Raman scattered photons by a sample to an avalanche photodiode (APD), said APD configured to generate an output signal responsive to the intensity of said Raman scattered photons incident thereon; cooling said APD by thermoelectric cooling, wherein said APD is biased in a sub-Geiger mode of operation; amplifying said output signal of said APD and passing said amplified output signal though a discriminator so as to reject at least one or more of amplifier noise and dark noise; and counting a number of discrete output pulses within a set operational range of said discriminator so as to determine a number of photons detected by said APD.
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14. An apparatus for Raman detection within a portable, integrated spectrometer instrument, comprising:
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an avalanche photodiode (APD) integrated on a chip, said APD configured to receive Raman scattered photons by a sample and generate an output signal responsive to the intensity of said Raman scattered photons incident thereon; a preamplifier integrated on said chip, said preamplifier configured to shape an output current pulse from said APD to a NIM standard pulse; an amplifier integrated on said chip, said amplifier configured to amplify said output signal of said APD and pass said amplified output signal though a discriminator integrated on said chip, so as to reject at least one or more of amplifier noise and dark noise; and a digitizer integrated on said chip, configured to count a number of discrete output pulses within a set operational range of said discriminator so as to determine a number of photons detected by said APD.
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Specification