MOPA with externally triggered passively Q-switched laser

• US 9,570,882 B2
• Filed: 03/27/2013
• Issued: 02/14/2017
• Est. Priority Date: 03/27/2013
• Status: Active Grant

• Current Assignee: Coherent LaserSystems GmbH & Co., KG (Coherent Corp.)
• Original Assignee: Coherent LaserSystems GmbH & Co., KG (Coherent Corp.)
• Inventors: Spiekermann, Stefan
• Primary Examiner(s): Zhang, Yuanda
• Assistant Examiner(s): CARTER, MICHAEL W
• Application Number:
  US13/851,275
• Publication Number:
  US 20160276801A1
• Time in Patent Office: 1,420 Days
• US Class Current: 1/1
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/094038 End pumping
• CPC Class Codes: H01S 3/094076 Pulsed or modulated pumping H01S3/1024 takes precedence
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/10046 Pulse repetition rate control H01S3/11 takes precedence
• CPC Class Codes: H01S 3/10084 Frequency control by seeding
• CPC Class Codes: H01S 3/1022 by controlling the optical pumping
• 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 3/113 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/1611 neodymium
• CPC Class Codes: H01S 3/1673 YVO4 [YVO]
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA

Abstract

In a master oscillator plus power amplifier (MOPA) system, the oscillator is a passively Q-switched laser. The laser is triggered into passively Q-switched operation by operating an optical switch to resonantly couple back into the laser amplified stimulated emission generated by the amplifier.

Claims

1. Optical apparatus, comprising:

a passively Q-switched diode-pumped laser-resonator including a solid-state gain-element for delivering laser pulses;

a diode-pumped optical amplifier for amplifying the laser pulses, the optical amplifier generating amplified stimulated emission in response to the diode-pumping; and

an optical switch located between the laser and the amplifier and arranged for selectively allowing the amplified stimulated emission to be resonantly coupled into the laser-resonator to seed the laser-resonator to cause a laser pulse to be delivered sooner than if the laser-resonator was not seeded.

2. The apparatus of claim 1 wherein the laser resonator has a length selected such that only a single lasing mode is possible within a gain-bandwidth of the solid-state gain element.

3. The apparatus of claim 1, wherein the optical amplifier is end-pumped by the diode-pumping.

4. The apparatus of claim 1, wherein the optical amplifier is a solid-state amplifier.

5. The apparatus of claim 1, where in the diode-pumping of the laser-resonator can be switched synchronously with the selective resonant coupling of the amplified stimulated emission.

6. The apparatus of claim 1, wherein the optical switch is an electro-optical switch.

7. The apparatus of claim 6, wherein the electro-optical switch includes a Pockels cell between first and second aligned polarizing elements.

8. The apparatus of claim 1, wherein the solid state gain-element is a neodymium-doped yttrium orthovanadate gain element.

9. A method for operating an optical apparatus, the apparatus including a diode-pumped passively Q-switched laser-resonator for delivering optical pulses, and a diode-pumped optical amplifier for amplifying the optical pulses, the optical amplifier generating forward and backward propagating amplified stimulated emission (ASE) in response to the diode-pumping thereof, the method comprising the steps of:

turning off the diode-laser pumping of the laser;

preventing backward propagating ASE from being coupled into the laser;

then,

resonantly coupling the backward-propagating ASE into the laser-resonator; and

turning on diode-laser pumping of the laser wherein the ASE that is backward-propagated in the laser-resonator functions to seed the laser resonator to cause one or more optical pulses to be delivered from the laser resonator sooner than if the laser-resonator was not seeded.

10. The method of claim 9, further including the step of turning off the diode-laser pumping of the laser after a predetermined number of the one or more optical pulses has been delivered.

11. A method for operating an optical apparatus, the apparatus including a diode-pumped passively Q-switched laser-resonator for delivering optical pulses, and a diode-pumped optical amplifier for amplifying the optical pulses, the optical amplifier generating forward and backward propagating amplified stimulated emission (ASE) in response to the diode-pumping thereof, the method comprising the steps of:

configuring the laser-resonator such that at a predetermined level of diode-pumping, delivery of pulses is not possible unless backward propagating ASE is resonantly coupled into the laser-resonator; and

selectively resonantly coupling backward-propagating ASE into the laser-resonator, thereby causing at least one or more optical pulses to be delivered from the laser resonator during the resonant coupling of the ASE.

12. The method of claim 11, further including the step of preventing the backward-propagating ASE from being coupled into the laser resonator after a predetermined number of the at least one optical pulses has been delivered.