GENERATION OF HIGH-POWER SPATIALLY-RESTRUCTURABLE SPECTRALLY-TUNABLE BEAMS IN A MULTI-ARM-CAVITY VECSEL-BASED LASER SYSTEM

• US 20190312408A1
• Filed: 12/19/2017
• Published: 10/10/2019
• Est. Priority Date: 12/21/2016
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Fallahi, Mahmoud, Wright, Ewan, Hessenius, Chris
• Granted Patent: US 10,511,145 B2
• Time in Patent Office: Days
• CPC Class Codes: H01S 2301/20 Lasers with a special output beam profile or cross-section, e.g. non-Gaussian
• 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 3/08027 by a filter, e.g. a Fabry-Perot filter is used for wavelength setting
• CPC Class Codes: H01S 3/0804 Transverse or lateral modes
• CPC Class Codes: H01S 3/08045 Single-mode emission
• CPC Class Codes: H01S 3/08054 Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation quarter-wave plates in a Q-switch laser H01S3/1124, H01S3/115
• CPC Class Codes: H01S 3/0815 having 3 reflectors, e.g. V-shaped resonators
• CPC Class Codes: H01S 3/082 defining a plurality of resonators, e.g. for mode selection or suppression
• CPC Class Codes: H01S 3/109 Frequency multiplication, e.g. harmonic generation
• CPC Class Codes: H01S 5/0092 for nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity
• CPC Class Codes: H01S 5/041 Optical pumping
• CPC Class Codes: H01S 5/0604 comprising a non-linear region, e.g. generating harmonics of the laser frequency
• CPC Class Codes: H01S 5/0651 Mode control
• CPC Class Codes: H01S 5/1021 Coupled cavities H01S5/14 takes precedence
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/142 which comprises an additional resonator
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• CPC Class Codes: H01S 5/18361 Structure of the reflectors, e.g. hybrid mirrors
• CPC Class Codes: H01S 5/4062 with an external cavity or using internal filters, e.g. Talbot filters
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

A collinear T-cavity VECSEL system generating intracavity Hermite-Gaussian modes at multiple wavelengths, configured to vary each of these wavelengths individually and independently. A mode converter element and/or an astigmatic mode converter is/are aligned intracavity to reversibly convert the Gaussian modes to HG modes to Laguerre-Gaussian modes, the latter forming the system output having any of the wavelengths provided by the spectrum resulting from nonlinear frequency-mixing intracavity (including generation of UV, visible, mid-IR light). The laser system delivers Watt-level output power in tunable high-order transverse mode distribution.

Claims

1. A laser source comprising:

a laser cavity network including first and second spatially-distinct cavity arms and a collinear portion, wherein the first and second spatially-distinct cavity arms share the collinear portion,

at least one of the first and second cavity arms containing, intracavity,

a corresponding gain medium including one of (i) a VECSEL-based laser gain medium, (ii) a solid-state gain medium, and (iii) a fiber amplifier and configured to provide amplification of light at a corresponding wavelength;

a first optical system, disposed across an axis of the at least one of the first and second cavity arms, to either refract or reflect light incident thereon while transforming a transverse distribution of said light that has traversed it, and

a second optical system disposed across said axis and characterized by optical losses, at the corresponding wavelength, that are non-uniformly distributed across the second optical system, the second optical system disposed between the corresponding gain medium and the first optical system;

wherein said laser source is configured to maintain, in operation, intracavity generation of light at the corresponding wavelength, said light having

a first transverse mode distribution in a first portion of the laser cavity network between the gain medium and the second optical system,

a second transverse mode distribution in a second portion of the laser cavity network between the second and first optical systems, and

a third transverse mode distribution in a third portion of the laser cavity network, the third portion being a remaining portion of the laser cavity network;

wherein the first, second, and third transverse mode distributions being different from one another.

2. A laser source according to claim 1, further comprising a non-linear optical conversion element in the collinear portion of the laser cavity network.

3. A laser source according to claim 2 further comprising

an optical element defining a spatial fold of a path of light propagating intracavity and forming, intracavity, first and second Rayleigh regions of first and second light portions of light,

wherein the first and second light portions respectively contain the first and second wavelengths, and

wherein said first and second Rayleigh regions overlap with one another in the spatial fold.

4. A laser source according to claim 3, wherein at least one of the following conditions is satisfied:

a) said optical element is not a reflector that terminates the cavity network while said optical element is an output coupler configured to transmit a portion of light, generated intracavity, to form a light output from the laser source, and

b) at least one of said first and second cavity arms contains an intracavity non-linear frequency conversion element.

5. A laser source according to claim 1, wherein at least one of the following conditions is satisfied:

(i) at least one of the first and second cavity arms is devoid of a gain medium, and

(ii) wherein the first transverse mode distribution is a Gaussian distribution;

the second transverse mode distribution is a Hermite-Gaussian distribution, and the third transverse mode distribution is a Laguerre-Gaussian distribution.

6. A laser source according to claim 1,

wherein each of the first and second cavity arms contains a respectively corresponding first and second VECSEL-based laser medium to cause independent lasing at respectively-corresponding first and second wavelengths, and

further comprising at least one wavelength tuning mechanism juxtaposed with the cavity network and configured to tune at least one of the first and second wavelengths independently from another of the first and second wavelengths while, at the same time, allowing the first and second wavelengths to become equal as a result of such tuning.

7. A laser source according to claim 1, wherein both the first and the second optical systems are located in the collinear portion of the laser cavity network.

8. A laser source according to claim 1, further comprising a system configured to cause said laser source to produce the laser output in a pulsed fashion.

9. A laser source according to claim 1, wherein the first cavity arm contains a corresponding gain medium element while the second cavity arm is devoid of a corresponding gain medium element,

wherein an end-reflector of the second cavity arm is partially transparent to light at a pump wavelength,

and further comprising a pump laser source that is configured to generate pump light at said pump wavelength and is positioned to deliver said pump light through said end reflector along an optical axis of the second cavity arm.

10-18. -18. (canceled)