Laser illumination systems and methods for dual-excitation wavelength non-linear optical microscopy and micro-spectroscopy systems

• US 8,792,156 B1
• Filed: 01/17/2012
• Issued: 07/29/2014
• Est. Priority Date: 01/17/2012
• Status: Active Grant

• Current Assignee: President and Fellows of Harvard College (Harvard Corporation), Arizona Board of Regents (University of Arizona)
• Original Assignee: President and Fellows of Harvard College (Harvard Corporation), Arizona Board of Regents (University of Arizona)
• Inventors: Xie, Xiaoliang Sunney, Kieu, Khanh, Peyghambarian, Nasser, Freudiger, Christian W., Fu, Dan
• Primary Examiner(s): Petkovsek, Daniel
• Application Number:
  US13/351,831
• Time in Patent Office: 924 Days
• Field of Search: 359326-332, 372/25, 356/301, 356/337, 356/342
• US Class Current: 359/327
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G01N 2021/653 Coherent methods [CARS]
• CPC Class Codes: G01N 2021/655 Stimulated Raman
• CPC Class Codes: G02B 21/002 Scanning microscopes scanning near field optical microscopes G01Q60/18
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control
• CPC Class Codes: G02B 21/16 adapted for ultraviolet illumination ; Fluorescence microscopes G02B21/0076 takes precedence
• CPC Class Codes: G02B 2207/114 Two photon or multiphoton effect
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• CPC Class Codes: G02F 1/354 Third or higher harmonic generation
• CPC Class Codes: G02F 1/37 for second-harmonic generation G02F1/3532 takes precedence
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/06791 Fibre ring lasers fibre laser gyrometers G01C19/72
• CPC Class Codes: H01S 3/10023 by functional association of additional optical elements, e.g. filters, gratings, reflectors
• CPC Class Codes: H01S 3/1118 Semiconductor saturable absorbers, e.g. semiconductor saturable absorber mirrors [SESAMs]; Solid-state saturable absorbers, e.g. carbon nanotube [CNT] based
• CPC Class Codes: H01S 3/1608 erbium
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/2391 : emitting at different wavelengths

Abstract

An illumination system is disclosed for providing dual-excitation wavelength illumination for non-linear optical microscopy and micro-spectroscopy. The illumination system includes a laser system, an optical splitting means, a frequency shifting system, and a picosecond amplifier system. The laser system includes a laser for providing a first train of pulses at a center optical frequency ω₁. The optical splitting means divides the first train of pulses at the center optical frequency ω₁ into two trains of pulses. The frequency shifting system shifts the optical frequency of one of the two trains of pulses to provide a frequency shifted train of pulses. The picosecond amplifier system amplifies the frequency shifted train of pulses to provide an amplified frequency-shifted train of pulses having a pulse duration of at least 0.5 picoseconds.

Claims

1. An illumination system for providing dual-excitation wavelength illumination for non-linear optical microscopy and micro-spectroscopy, said illumination system comprising:

a laser system including a laser oscillator for providing a first train of pulses at a center optical frequency ω

₁;

an optical splitting means for dividing the first train of pulses at the center optical frequency ω

₁ into a first split train of pulses and a second split train of pulses;

a frequency shifting system for shifting the optical frequency of the first split train of pulses to provide a frequency shifted train of pulses; and

a picosecond amplifier system for amplifying the frequency shifted train of pulses to provide an amplified frequency-shifted train of pulses having a pulse duration of at least 0.5 picoseconds.

2. The illumination system as claimed in claim 1, wherein said picosecond amplifier is a narrowband amplifier.

3. The illumination system as claimed in claim 2, wherein said narrowband amplifier is tunable to provide that the difference frequency of the amplified frequency-shifted train of pulses and the second split train of pulses may be varied.

4. The illumination system as claimed in claim 2, wherein said narrowband amplifier system includes a narrowband filter.

5. The illumination system as claimed in claim 2, wherein said narrowband amplifier system includes a plurality of amplifiers in series.

6. The illumination system as claimed in claim 1, wherein said laser system includes a high power oscillator.

7. The illumination system as claimed in claim 1, wherein said laser system includes a low power oscillator and an amplifier.

8. The illumination system as claimed in claim 1, wherein said illumination system further includes a laser amplifier for amplifying the second split train of pulses.

9. The illumination system as claimed in claim 1, wherein said frequency shifting system includes a highly non-linear fiber.

10. The illumination system as claimed in claim 1, wherein said frequency shifting system includes a photonic crystal fiber.

11. The illumination system as claimed in claim 1, wherein said frequency shifting system further includes a laser amplifier.

12. The illumination system as claimed in claim 1, wherein said picosecond amplifier is a chirp amplifier to provide an amplified frequency-shifted train of pulses having pulses with a temporally evolving instantaneous frequency over the picosecond pulse duration.

13. The illumination system as claimed in claim 12, wherein said chirped amplifier system includes a chirp unit and an amplifier.

14. The illumination system as claimed in claim 13, wherein said chirped amplifier system further includes a broadband filter.

15. The illumination system as claimed in claim 14, wherein system further includes a chirp control system in the second split train of pulses.

16. The illumination system as claimed in claim 1, wherein system further includes:

a combiner for combining the amplified frequency-shifted train of pulses and the second split train of pulses from the optical splitting means; and

adjusting means for adjusting a time delay between the amplified frequency-shifted train of pulses and the second split train of pulses with sub-picosecond precision to provide a collinear output of the dual-excitation wavelength illumination for the non-linear optical microscopy or micro-spectroscopy system.

17. The illumination system as claimed in claim 1, wherein said laser system is one of a Ytterbium fiber laser and an Erbium fiber laser.

18. The illumination system as claimed in claim 1, wherein said laser system is a Titanium Sapphire laser.

19. The illumination system as claimed in claim 1, wherein said picosecond amplifier system is one of an Erbium fiber amplifier, a Ytterbium fiber amplifier, a Thulium fiber amplifier, and a Holmium fiber amplifier.

20. The illumination system as claimed in claim 1, wherein the output of the picosecond amplifier system is frequency doubled (SHG) or tripled (THG).

21. The illumination system as claimed in claim 1, wherein the second split train of pulses from the optical splitting means is frequency doubled (SHG) or tripled (THG).