Surface emitting laser with an integrated absorber

• US 20070189350A1
• Filed: 03/19/2007
• Published: 08/16/2007
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: Heiko Unold, Ian Young, Rudiger Paschotta, Silke Schon, Ursula Keller
• Inventors: Unold, Heiko, Young, Ian, Schon, Silke, Paschotta, Rudiger, Keller, Ursula
• Granted Patent: US 7,729,393 B2
• Time in Patent Office: Days
• US Class Current: 372/50.124
• CPC Class Codes: G06F 1/105 in which the distribution is at least partially optical
• 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 3/0604 in the form of a plate or disc
• CPC Class Codes: H01S 3/0615 Shape of end-face
• CPC Class Codes: H01S 3/0627 the resonator being monolithic, e.g. microlaser
• CPC Class Codes: H01S 3/094084 with pump light recycling, i.e. with reinjection of the unused pump light, e.g. by reflectors or circulators
• CPC Class Codes: H01S 3/1115 using intracavity saturable absorbers
• CPC Class Codes: H01S 3/1118 Semiconductor saturable absorbers, e.g. semiconductor saturable absorber mirrors [SESAMs]; Solid-state saturable absorbers, e.g. carbon nanotube [CNT] based
• CPC Class Codes: H01S 5/024 Arrangements for thermal management
• CPC Class Codes: H01S 5/041 Optical pumping
• CPC Class Codes: H01S 5/0609 acting on an absorbing region, e.g. wavelength convertors
• CPC Class Codes: H01S 5/0657 Mode locking, i.e. generation of pulses at a frequency corresponding to a roundtrip in the cavity
• 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 5/18302 comprising an integrated optical modulator
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/18388 Lenses
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

A surface emitting laser (SEL) with an integrated absorber. A lower mirror and an output coupler define a laser cavity of the SEL. A monolithic gain structure positioned in the laser cavity includes a gain region and an absorber, wherein a saturation fluence of the absorber is less than a saturation fluence of the gain region.

Claims

1. A surface emitting laser (SEL), comprising:

an absorber integrated with a gain region in a monolithic gain structure resulting in the absorber and gain region being operable with similar mode spot sizes;

the absorber having a reduced saturation fluence relative to a saturation fluence of the gain region; and

wherein the SEL emits passively mode-locked laser output while the absorber and gain region are operating with the similar mode spot sizes.

2. The SEL of claim 1, wherein the absorber comprises quantum dots.

3. The SEL of claim 2, wherein the quantum dots comprising the absorber have a density determined to reduce the saturation fluence of the absorber relative to the saturation fluence of the gain region in an amount sufficient to allow the SEL to emit passively mode-locked laser output while the absorber and gain region are operating with similar mode spot sizes.

4. The SEL of claim 3, wherein the determined density is obtained by arranging the quantum dots in layers.

5. The SEL of claim 4, wherein the determined density is obtained by separating the layers of quantum dots with spacer layers, the spacer layers being transparent.

6. The SEL of claim 4, wherein the layers of quantum dots are positioned on a standing wave pattern during operation of the SEL to adjust the saturation fluence of the absorber relative to the saturation fluence of the gain region in an amount sufficient to allow the SEL to emit passively mode-locked laser output while the absorber and gain region are operating with similar mode spot sizes.

7. The SEL of claim 2, wherein the quantum dots comprising the absorber have a size measured based on a diameter at the base of the quantum dot and a height of the quantum dot.

8. The SEL of claim 7, wherein the size of the quantum dots comprising the absorber varies, the base diameters of the quantum dots measuring from 10 to 50 nanometers and the heights of the quantum dots measuring from 2-10 nanometers.

9. The SEL of claim 7, wherein the quantum dots comprising the absorber have a density determined to reduce the saturation fluence of the absorber relative to the saturation fluence of the gain region in an amount sufficient to allow the SEL to emit passively mode-locked laser output while the absorber and gain region are operating with similar mode spot sizes, wherein the determined density is obtained by varying the size of the quantum dots.

10. The SEL of claim 7, wherein a distribution of the quantum dot sizes is selected to produce a desired spectral width of absorption in the absorber, the desired spectral width allowing the SEL to emit passively mode-locked laser output while the absorber and gain region are operating with similar mode spot sizes.

11. The SEL of claim 2, wherein the gain region in the monolithic gain structure is electrically pumped.

12. The SEL of claim 11, wherein the monolithic gain structure includes a lower mirror, wherein electrical pumping is provided to the SEL at least in part via a contact coupled to the lower mirror.

13. The SEL of claim 12, wherein electrical pumping is provided to the SEL at least in part via a contact coupled to one of a spacer, anti-reflective, and index-matching layers in the SEL.

14. The SEL of claim 1, wherein the monolithic gain structure is fabricated from a substrate in a single fabrication process.

15. An apparatus, comprising:

a quantum dot semiconductor saturable absorber mirror;

an output coupler, the quantum dot saturable mirror and the output coupler defining a laser cavity; and

a laser medium positioned within the laser cavity.

16. The apparatus of claim 15 wherein the quantum dot semiconductor saturable absorber mirror is integrated with the laser medium.

17. The apparatus of claim 16 wherein the output coupler is a curved reflector integrated with the laser medium.