Optically pumped tunable VCSEL employing geometric isolation
An optically pumped tunable VCSEL swept source module has a VCSEL and a pump, which produces light to pump the VSCEL, wherein the pump is geometrically isolated from the VCSEL. In different embodiments, the pump is geometrically isolated by defocusing light from the pump in front of the VCSEL, behind the VCSEL, and/or by coupling the light from the pump at an angle with respect to the VCSEL. In the last case, angle is usually less than 88 degrees. There are further strategies for attacking pump noise problems. Pump feedback can be reduced through (1) Faraday isolation and (2) geometric isolation. Single frequency pump lasers (Distributed feedback lasers (DFB), distributed Bragg reflector lasers (DBR), Fabry-Perot (FP) lasers, discrete mode lasers, volume Bragg grating (VBG) stabilized lasers can eliminate wavelength jitter and amplitude noise that accompanies mode hopping.
1. An optically pumped tunable vertical cavity surface emitting laser (VCSEL) swept source module, comprising:
a tunable VCSEL,
a lens configured to collimate a VCSEL beam emitted by the VCSEL;
a pump configured to produce pump light that is transmitted through the lens, wherein an optical axis of the pump light is offset with respect to an optical axis of the lens; and
a dichroic filter configured such that the pump light and a reflected pump light are transmitted through the dichroic filter, wherein the reflected pump light is the pump light reflected from the VCSEL.
2. The module of claim 1 , wherein the pump is a VBG or FBG stabilized laser, a discrete mode laser, a DFB laser, FP laser or a DBR laser.
3. The module of claim 1 , further comprising an SOA for amplifying the VCSEL beam.
4. The module of claim 1 , further comprising a beam block for intercepting the reflected pump light.
5. The module of claim 1 , further comprising an integrated dichroic filter, an SOA, and an isolator.
6. The module of claim 1 , wherein a pump angle between the pump light coupled into the VCSEL and pump light reflected from the VCSEL is greater than a divergence angle of the pump light coupled into the VCSEL.
7. The module of claim 1 , wherein the pump light is coupled into the VCSEL such that the optical axis of the pump light is at an angle relative to a surface of a gain substrate of the VCSEL.
8. The module of claim 7 , wherein the angle is less than 88 degrees.
9. The module of claim 7 , wherein the angle is less than 80 degrees.
10. The module of claim 7 , wherein the angle is greater than 75 degrees.
11. A method for optically pumping a VCSEL, comprising:
producing pump light with a pump source; and
coupling the pump light into the VCSEL from the pump source by transmitting the pump light through a lens, wherein the lens is configured to collimate light emitted by the VCSEL and wherein an optical axis of the pump light is offset with respect to an optical axis of the lens, and wherein coupling the pump light into the VCSEL comprises coupling the pump light through a dichroic filter configured such that the pump light and a reflected pump light are transmitted through the dichroic filter, wherein the reflected pump light is the pump light reflected from the VCSEL.
12. The method of claim 11 , wherein the pump light is coupled into the VCSEL such that the optical axis of the pump light is at an angle less than 88 degrees relative to a surface of a gain substrate of the VCSEL.
13. The method of claim 11 , wherein the pump source is a VBG or FBG stabilized laser, a discrete mode laser, a DFB laser, FP laser or a DBR laser.
14. An optically pumped tunable vertical cavity surface emitting laser (VCSEL) swept source module, comprising:
a tunable VCSEL;
a pump for producing pump light to pump the VCSEL, wherein the pump is a single frequency pump;
a lens configured to collimate light emitted by the VCSEL, wherein an optical axis of the pump light is offset with respect to an optical axis of the lens, and
a dichroic filter configured such that the pump light and a reflected pump light are transmitted through the dichroic filter, wherein the reflected pump light is the pump light reflected from the VCSEL.
15. The module of claim 14 , wherein the pump is a distributed feedback laser.
16. The module of claim 14 , wherein the pump is a distributed Bragg reflector laser.
17. The module of claim 14 , wherein the pump is a discrete mode laser.