METHOD OF AND APPARATUS FOR GENERATING ULTRA-SHORT TIME-DURATION LASER PULSES

• US 3,736,526 A
• Filed: 08/07/1972
• Issued: 05/29/1973
• Est. Priority Date: 05/14/1971
• Status: Expired due to Term

• Current Assignee: William W. Simmons
• Original Assignee: William W. Simmons
• Inventors: Simmons, William W.
• Primary Examiner(s): Sikes, William L.
• Application Number:
  US05/278,373
• Time in Patent Office: 295 Days
• Field of Search: 331/94.5
• US Class Current: 372/18
• 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 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 3/1109 Active mode locking
• CPC Class Codes: H01S 3/115 using intracavity electro-optic devices

Abstract

Both a method and an apparatus are disclosed for generating laser pulses having a time duration on the order of subnanoseconds. These light pulses also have a high output power. They are generated by causing a laser to lase and removing the bulk of the radiation contained in the laser cavity. The remaining radiation or light extends over only a short length of the cavity. This light pulse is mode locked, that is it consists of individual Fourier components of the proper phase so that the short light pulse retains its shape while being amplified again in the laser cavity. This short-duration light pulse may then be made to issue from the cavity. Alternatively, the amplified light may be made to issue as a pulse train or set of pulses. Finally, a single pulse may be utilized for mode locking another laser where the ultra-short time-duration pulse may be amplified again. This may be considered priming and subsequent mode locking of the second laser.

Claims

1. Apparatus for generating an ultra-short time-duration pulse in a first laser and injecting it into a second laser for mode locking said second laser, said apparatus comprising:

a. a first optical cavity defined by a first pair of substantially completely reflecting mirrors;

b. a first laser disposed in said first cavity;

c. a second optical cavity defined by a second pair of substantially completely reflecting mirrors, said second cavity intersecting said first cavity;

d. a second laser disposed in said second cavity;

e. means for pumping said lasers to cause them to lase;

f. a first and a second electro-optical element disposed in said first cavity;

g. a third and a fourth electro-optical element disposed in said second cavity, each of said elements being capable of changing the polarization of light passing therethrough in response to an applied voltage;

h. a first birefringent prism disposed in said first cavity and at the intersection of said first and second cavities, said first prism being normally arranged for refracting light having a first predetermined polarization between said first pair of mirrors and being capable of refracting light having a second predetermined polarization into said second cavity;

i. a second birefringent element disposed in said second cavity, said second prism being normally arranged for refracting light having a first predetermined polarization between said second pair of mirrors and being capable of refracting light having a second predetermined polarization out of said cavity; and

j. voltage generators coupled to said elements for applying to said first element a short time duration pulse, whereby the polarization of the light passing therethrough is changed from said first to said second predetermined polarization so as to cause said first prism to refract said light out of said first cavity and into said second cavity, and for applying a voltage to said second element after the pulse remaining in said first cavity has been amplified for changing the polarization of the light passing therethrough into said second predetermined polarization so as to cause said amplified pulse to be injected into said second cavity, and said voltage generator applying to said third and fourth elements a voltage so as to raise the Q of said second cavity and permitting said second cavity to receive and amplify said injected pulse and finally to apply a voltage to one of said second and third elements to cause the amplified pulse to issue from said second cavity.

2. Apparatus as claimed in claim 1 wherein said electrooptical elements are Kerr cells.

3. Apparatus as claimed in claim 1 wherein said electrooptical elements are Pockels cells.