OCT System with Bonded MEMS Tunable Mirror VCSEL Swept Source

Abstract

A microelectromechanical systems (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) in which the MEMS mirror is a bonded to the active region. This allows for a separate electrostatic cavity, that is outside the laser's optical resonant cavity. Moreover, the use of this cavity configuration allows the MEMS mirror to be tuned by pulling the mirror away from the active region. This reduces the risk of snap down. Moreover, since the MEMS mirror is now bonded to the active region, much wider latitude is available in the technologies that are used to fabricate the MEMS mirror. This is preferably deployed as a swept source in an optical coherence tomography (OCT) system.

What is claimed is: 
     
         1 . A MEMS tunable VCSEL, comprising:
 an active region substrate having active layers that amplify light; and   an optical membrane device that is attached to the active region substrate.   
     
     
         2 . A VCSEL as claimed in  claim 1 , further comprising a spacer device that separates the active region substrate from the optical membrane device. 
     
     
         3 . A VCSEL as claimed in  claim 1 , wherein the active region substrate further comprises a rear mirror. 
     
     
         4 . A VCSEL as claimed in  claim 3 , wherein the rear mirror is a layer within the active region substrate. 
     
     
         5 . A VCSEL as claimed in  claim 3 , wherein the rear mirror is deposited in an optical port formed into the active region substrate. 
     
     
         6 . A VCSEL as claimed in  claim 3 , when the rear mirror is a dichroic mirror that is reflective to the wavelengths of light amplified by the active region substrate and transmissive to wavelengths of light generated by a pump laser. 
     
     
         7 . A VCSEL as claimed in  claim 1 , wherein the optical membrane device comprises a substrate layer, a device layer, in which a membrane is patterned, and intervening insulating layer. 
     
     
         8 . A VCSEL as claimed in  claim 7 , wherein the insulating layer defines an electrostatic cavity. 
     
     
         9 . A VCSEL as claimed in  claim 1 , wherein an optical membrane of the optical membrane device is deflected in a direction away from the active region substrate. 
     
     
         10 . A VCSEL as claimed in  claim 1 , wherein an optical membrane of the optical membrane device includes a curved mirror structure. 
     
     
         11 . A method for fabricating a MEMS tunable VCSEL, comprising:
 providing an active region substrate having active layers that amplify light; and   bonding an optical membrane device to the active region substrate.   
     
     
         12 . A method as claimed in  claim 11 , wherein the bonding the optical membrane device to the active region substrate comprises thermocompression bonding the optical membrane device to the active region substrate. 
     
     
         13 . A method as claimed in  claim 11 , wherein the bonding the optical membrane device to the active region substrate comprises solder bonding the optical membrane device to the active region substrate. 
     
     
         14 . An integrated VCSEL swept source system, comprising:
 an optical bench; and   a MEMS tunable VCSEL installed on the optical bench that emits a swept optical signal that propagates parallel to a top surface of the optical bench.   
     
     
         15 . A system as claimed in  claim 14 , further comprising a focusing lens secured to the optical bench for coupling the swept optical signal into an optical fiber. 
     
     
         16 . A system as claimed in  claim 14 , further comprising a hermetic package containing the optical bench. 
     
     
         17 . A system as claimed in  claim 16 , further comprising a thermoelectric cooler installed between the optical bench and in the hermetic package to control a temperature of the optical bench. 
     
     
         18 . A system as claimed in  claim 14 , further comprising a laser pump installed on the optical bench for generating pump light for optically pumping an active layer within the MEMS tunable VCSEL. 
     
     
         19 . A system as claimed in  claim 18 , further comprising an isolator between the laser pump and the MEMS tunable VCSEL for preventing back reflections into the laser pump. 
     
     
         20 . A system as claimed in  claim 18 , wherein the swept optical signal is taken from one side of the MEMS tunable VCSEL and the pump light is coupled into the other side of the MEMS tunable VCSEL. 
     
     
         21 . A system as claimed in  claim 18 , wherein the swept optical signal is taken from the same side of the MEMS tunable VCSEL as the pump light is coupled into the MEMS tunable VCSEL. 
     
     
         22 . A system as claimed in  claim 14 , further comprising a semiconductor optical amplifier that is installed on the optical bench that amplifies the swept optical signal. 
     
     
         23 . A system as claimed in  claim 22 , further comprising two isolators on either side of the semiconductor optical amplifier. 
     
     
         24 . A system as claimed in  claim 23 , wherein the amplified swept optical signal from the semiconductor optical amplifier is returned to propagate through the MEMS tunable VCSEL. 
     
     
         25 . A system as claimed in  claim 23 , further comprising a polarization beam splitter for directing the amplified swept optical signal from the semiconductor optical amplifier to be coupled into the MEMS tunable VCSEL. 
     
     
         26 . A system as claimed in  claim 14 , wherein the MEMS tunable VCSEL is electrically pumped. 
     
     
         27 . An optical coherence analysis system, comprising:
 an interferometer that divides a swept optical signal between a reference arm and a sample arm and combines optical signals returning from the reference arm and the sample arm to generate an interference signal;   a MEMS tunable VCSEL that generates the swept optical signal, the MEMS tunable VCSEL including an active region substrate having active layers that amplify light, and an optical membrane device that is attached to the active region substrate; and   a detection system that detects the interference signal.