Generating laser pulses and spectroscopy using the temporal talbot effect

Patent metadata

Field	Value
Publication number	US-10297974-B2
Application number	US-201815891343-A
Country	US
Kind code	B2
Filing date	Feb 7, 2018
Priority date	Feb 13, 2017
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A method of generating laser pulses ( 1 ) includes: creating a circulating light field in resonator device ( 11 ) having resonator length L and an intra-cavity dispersion and configured for supporting light field resonator modes, and generating a pulse train of laser pulses ( 1 ) by a mode-locking mechanism. Laser pulses ( 1 ) are generated with a repetition frequency and provide a frequency comb with carrier frequency ω o and comb modes in frequency space. The intra-cavity dispersion is selected such that round trip phases ϕ have a dependency on frequency ω according to
ϕ ⁡ ( ω ) = π ⁢ ⁢ m ⁡ ( 1 + 4 ⁢ ⁢ ω - ω 0 m ⁢ ⁢ ω r - 1 ) + L c ⁢ ω 0
wherein m is an integer providing effective repetition rate (mω r ) in combination with mode spacing ω r at optical carrier frequency (ω o ), and the mode-locking mechanism provides a coupling of the resonator modes whereby frequency difference (Δn=ω n+1 −ω n ) between neighboring mode frequencies (ω n , ω n+1 ) is a linear function of mode frequency number n. Furthermore, a spectroscopy method for investigating a sample, a laser pulse source apparatus and a spectroscopy apparatus are described.

First claim

The invention claimed is:

1. A method of generating laser pulses, comprising the steps of
creating a circulating light field in a resonator device having a resonator length L and an intra-cavity dispersion and being configured for supporting a plurality of resonator modes of the light field, and
generating a pulse train of the laser pulses by a mode-locking mechanism, wherein the laser pulses provide a frequency comb with a carrier frequency ω o and plurality of comb modes in frequency space, wherein
the intra-cavity dispersion is selected such that round trip phases ϕ have a dependency on frequency ω according to

ϕ
⁡

(
ω
)

=

π
⁢

⁢

m
⁡

(

1
+

4
⁢

ω
-

ω
0

m
⁢

⁢

ω
r

-
1

)

+

L
c

⁢

ω
0

wherein m is an integer that gives an effective repetition rate mω r of the laser pulses in combination with a mode spacing ω r at the optical carrier frequency ω o , and
the mode-locking mechanism provides a coupling of the resonator modes such that a frequency difference (Δ n =ω n+1 −ω n ) between neighboring mode frequencies (ω n , ω n+1 ) is a linear function of an integer mode frequency number n.

2. The method according to claim 1 , wherein the mode frequency ω n with the mode frequency number n is given by

ω
n

=

ω
0

+

(

n
+

n
2

m

)

⁢

ω
r

.

3. The method according to claim 2 , wherein the intra-cavity dispersion is selected such that the k-th derivative of the comb mode phase at the carrier frequency ω o is given by

ϕ

ω
0

(
k
)

=

(

-
1

)

k
+
1

⁢

2
k

⁢

(

2
⁢

⁢
k

-
3

)

!!

⁢

⁢
π

m

k
-
1

⁢

ω
r
k

wherein k is the order of intra-cavity dispersion.

4. The method according to claim 1 , wherein the frequency difference between neighboring comb frequencies (Δ n =ω n+1 −ω n ) is in a radio frequency range.

5. The method according to claim 1 , wherein the intra-cavity dispersion is set with at least one fiber Bragg grating, at least one intracavity prism and/or at least one intracavity grating included in the resonator device.

6. The method according to claim 1 , wherein the resonator device is a fiber ring laser.

7. A spectroscopy method for obtaining a spectral response of a sample, comprising the steps of
generating a pulse train of laser pulses with a method according to claim 1 ,
applying the laser pulses on the sample under investigation,
detecting the laser pulses with a detector device,
analyzing a detector signal of the detector device for obtaining beat signals created by the comb modes of the pulse train of laser pulses, and
determining the spectral response of the sample from the beat signals.

8. The spectroscopy method according to claim 7 , further comprising the steps of
detecting a reference portion of the pulse train of laser pulses without an application on the sample with the detector device, and
analyzing a reference detector signal of the detector device for obtaining reference beat signals created by the comb modes of the reference portion of the pulse train of laser pulses, wherein
the

Assignees

• Max Planck Gesellschaft

Inventors

• Udem Thomas
• Ozawa Akira

Classifications

• H01S3/0057

  Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108) · CPC title

• H01S3/1109

  Active mode locking · CPC title

• H01S3/0675

  Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers · CPC title

• G01J3/0218

  using optical fibers · CPC title

• G01J2003/282

  Modified CCD or like · CPC title