Optical signal processing with modelocked lasers

• US 9,711,932 B2
• Filed: 09/08/2015
• Issued: 07/18/2017
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Fermann, Martin, Hartl, Ingmar, Ruehl, Axel
• Primary Examiner(s): Lapage, Michael P
• Application Number:
  US14/847,139
• Publication Number:
  US 20150380892A1
• Time in Patent Office: 679 Days
• CPC Class Codes: G01J 2003/102 Plural sources
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/45 Interferometric spectrometry
• CPC Class Codes: G01N 2021/3595 using FTIR
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B
• CPC Class Codes: G01N 21/636 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 Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/105 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity lengthH01S3/10076, H01S3/13 take precedence
• CPC Class Codes: H01S 3/1068 using an acousto-optical device
• CPC Class Codes: H01S 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers

Abstract

The invention relates to scanning pulsed laser systems for optical imaging. Coherent dual scanning laser systems (CDSL) are disclosed and some applications thereof. Various alternatives for implementation are illustrated. In at least one embodiment a coherent dual scanning laser system (CDSL) includes two passively modelocked fiber oscillators. In some embodiments an effective CDSL is constructed with only one laser. At least one embodiment includes a coherent scanning laser system (CSL) for generating pulse pairs with a time varying time delay. A CDSL, effective CDSL, or CSL may be arranged in an imaging system for one or more of optical imaging, microscopy, micro-spectroscopy and/or THz imaging.

Claims

1. A coherent dual scanning laser system (CDSL), comprising:

first and second passively mode locked oscillators, said oscillators configured to operate at slightly different repetition rates, such that a difference δ

f_r in repetition rates is small compared to values f_r1 and f_r2 of the repetition rates of said first and second oscillators, said first oscillator generating multiple frequency lines separated by f_r1 within a first optical emission envelope and said second oscillator generating multiple frequency lines separated by f_r2 within a second optical emission envelope;

first and second cw reference lasers operating at respective cw reference frequencies f_x and f_y, each of said first and second cw reference lasers being optically connected with each of said first and second oscillators, and producing outputs located within the emission envelope of each of said oscillators,

said first cw reference laser having a frequency line separated by f_b1 from a frequency line of said first oscillator and separated by f_b2 from a frequency line of said second oscillator;

said second cw reference laser having a frequency line separated by f_b3 from a frequency line of said first oscillator and separated by f_b4 from a frequency line of said second oscillator;

said cw reference lasers and said oscillators arranged to generate RF beat frequencies corresponding to Δ

f₂=f_b1−

f_b2 and Δ

f₁=f_b3−

f_b4;

wherein said RF beat frequencies are locked to external RF reference signals via phase locked loops.

2. The CDSL according to claim 1, wherein said laser system is arranged with measurement or imaging equipment for one or more of optical imaging, microscopy, spectroscopy, micro-spectroscopy, THz imaging, emission spectroscopy, Raman spectroscopy, stimulated Raman spectroscopy, Raman spectroscopy imaging, and multidimensional spectroscopy.

3. The CDSL according to claim 1, further comprising:

a phase-locked loop to control the repetition rate of one of said oscillators.

4. The CDSL according to claim 1, further comprising:

a phase locked loop and an f−

2f interferometer to control at least the carrier envelope offset frequency of one of said oscillators.

5. The CDSL according to claim 1, wherein said mode locked oscillators comprise a mode locked solid-state, fiber or diode laser oscillator.

6. The CDSL according to claim 1, wherein said mode locked oscillator comprises a Nd, Yb, Tm or Er fiber oscillator.

7. The CDSL according to claim 1, said system comprising at least one fiber amplifier for amplifying one or more oscillator outputs.