Transient grating time resolved luminescence measurements

Patent metadata

Field	Value
Publication number	US-2016356644-A1
Application number	US-201515117598-A
Country	US
Kind code	A1
Filing date	Feb 5, 2015
Priority date	Feb 10, 2014
Publication date	Dec 8, 2016
Grant date	—

Abstract

A transient grating (TG) is used as an optical gating element with sub-picosecond time resolution for luminescence measurements from a photo-detector array. The transient grating is formed in a gate medium by one or more pulsed gate beams. For photoluminescence measurements such as photoluminescence spectroscopy or imaging, a source is excited by a pulsed excitation beam, and the pulsed gate beams are synchronized to the pulsed excitation beam with an adjustable delay between the excitation of the source and the formation of the TG. Moreover, a source or its spectra can be imaged at two different regions of the photo-detector array at two different times spaced in time by a selected duration of time with sub-picosecond resolution over a range of a nanosecond or more. A beam from the source is deflected to the different regions by changing the frequency or geometry of the pulsed gate beams.

First claim

1 . A method of measuring light emitted by a source, said method comprising:
(a) imaging light from the source onto a photo-detector array at a selected instant in time by disposing a gate medium between the source and the photo-detector array and also illuminating the gate medium with at least one pulsed gate beam to form a transient grating in the gate medium at the selected instant in time; and (b) collecting measurements from the photo-detector array of the light imaged onto the photo-detector array.

2 . The method as claimed in claim 1 , wherein said at least one pulsed gate beam is produced by a femtosecond pulsed laser and the transient grating persists in the gate medium for less than one picosecond so that the measurements collected from the photo-detector array resolve the light imaged from the source with sub-picosecond time resolution.

3 . The method as claimed in claim 1 , wherein the pulsed gate beam is chirped to sweep the imaged light from the source across the photo-detector array.

4 . The method as claimed in claim 1 , wherein the gate medium is configured as an image plate, and the transient grating occupies a fraction of the image plate and sweeps across the image plate.

5 . The method as claimed in claim 1 , which includes illuminating the gate medium with two pulsed gate beams crossing each other in the gate medium to form an interference pattern in the gate medium that induces the transient grating in the gate medium.

6 . The method as claimed in claim 1 , which includes exciting the source with a pulsed excitation beam, and synchronizing said at least one pulsed gate beam to the pulsed excitation beam with an adjustable delay

7 . The method as claimed in claim 6 , which includes repeating the imaging of light from the source onto the photo-detector array and the collecting of measurements from the photo-detector array of the light imaged onto the photo-detector array for different adjusted delays and combining the measurements collected from the photo-detector array to construct a graph of the light imaged from the source as a function of time since the excitation of the source.

8 . The method as claimed in claim 1 , which includes imaging light at a first instant in time to form a first image of light from the source on a first region of the photo-detector array by forming a first transient grating at the first instant in time in the gate medium, and then imaging light at a second instant in time to form a second image of light from the source on a second region of the photo-detector array by forming a second transient grating at the second instant in time in the gate medium, and comparing the measurements collected from the photo-detector array of the light imaged onto the photo-detector array at the first region to measurements collected from the photo-detector array of the light imaged onto the photo-detector at the second region.

9 . The method as claimed in claim 8 , which includes splitting a pulsed gate source beam into a first part and a second part, splitting the first part to produce a first gate beam and a second gate beam, and illuminating the gate medium with the first gate beam and the second gate beam at a first crossing angle to produce the first transient grating in the gate medium, and delaying the second part by a selected delay and producing a third gate beam and a fourth gate beam from the delayed second part, and illuminating the gate medium with the third gate beam and the fourth gate beam at a second crossing angle to produce the second transient grating in the gate medium.

10 . The method as claimed in claim 8 , which includes repeating the imaging of light from the source onto the photo-detector array and the collecting of measurements from the photo-detector array of the light imaged onto the photo-detector array for different adjustable delays between the first instant in time and the second instant in time and the comparing of the measurements collected from the photo-detector array of the light imaged onto the photo-detector array at the first region to measurements collected from the photo-detector array of the light imaged onto the photo-detector array at the second region for different adjusted intervals of time between the first instant in time and the second instant of time, and computing statistics of the measurements.

11 . The method as claimed in claim 1 , which further includes disposing a polychromator between the source and the photo-detector array so that the light imaged from the source onto the photo-detector array includes a spectrum.

12 . The method as claimed in claim 11 , wherein the spectrum includes wavelengths of light in the range of ultraviolet to infrared.

13 . A system for measuring light emitted by a source, said system comprising:
(a) a photo-detector array for detecting an image of the light emitted by the source; (b) a gate medium disposed between the source and the photo-detector array so that the image of the light from the source is produced on the photo-detector array when a transient grating is produced in the gate medium; and (c) a pulsed gate beam source for producing at least one pulsed gate beam to form the transient grating in the gate medium.

14 . The system as claimed in claim 13 , wherein the gate beam source is a femtosecond pulsed laser and the transient grating persists in the gate medium for less than one picosecond so that the measurements collected from the photo-detector array resolve the light imaged from the source with sub-picosecond time resolution.

15 . The system as claimed in claim 13 , which includes at least one beam splitter for splitting a pulsed beam from the gate beam source into two pulsed gate beams that cross each other in the gate medium to form an interference pattern in the gate medium that induces the transient grating in the gate medium.

16 . The system as claimed in claim 13 , which includes a pulsed excitation beam source synchronized to the pulsed gate beam source, and an adjustable delay line for adjusting delay of said at least one pulsed gate beam with respect to the pulsed excitation beam.

17 . The system as claimed in claim 16 , wherein the pulsed excitation beam source is a tunable optical parametric amplifier excited by the pulsed gate beam source.

18 . The system as claimed in claim 13 , wherein said at least one pulsed gate beam produces a first transient grating in the gate medium and a first image of the light from the source on the photo-detector array, and which includes a beam splitter and an adjustable delay line for producing another pulsed gate beam delayed by a selected duration of time from said at least one pulsed gate beam gate pulse, said another pulsed gate beam being directed to the gate medium to produce a second transient grating in the gate medium, so that the photo-detector array detects a second image of the light emitted by the source, and the second image of the light emitted by the source is located on a different region of the photo-detector array than the first image of the light emitted by the source.

19 . The system as claimed in claim 18 , which includes a first beam splitter for splitting said at least one pulsed gate beam into a first part and a second part, a second beam splitter for splitting the first part to produce a first gate beam and a second gate beam directed to the gate medium at a first crossing angle to produce the first transient grating in the gate medium, and an adjustable delay line for delaying the second part by a selected delay and a third beam spl

Assignees

• Victoria Link Ltd

Inventors

• Hodgkiss Justin M
• Chen Kai

Classifications

• G01J1/4228 Primary

  arrangements with two or more detectors, e.g. for sensitivity compensation · CPC title

• G01N21/636 Primary

  using an arrangement of pump beam and probe beam; using the measurement of optical non-linear properties; (non-linear optics per se G02F1/35) · CPC title

• G01N21/6408

  with measurement of decay time, time resolved fluorescence · CPC title

• G01J3/0232

  using shutters · CPC title

• G01N2201/0696

  Pulsed · CPC title