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 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 method for fabricating a microelectromechanical systems (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL), the method comprising:
 providing an active region substrate having active layers that amplify light; and   bonding an optical membrane device to the active region substrate.   
     
     
         2 . A method as claimed in  claim 1 , wherein bonding the optical membrane device to the active region substrate comprises metal bonding the optical membrane device to the active region substrate. 
     
     
         3 . A method as claimed in  claim 1 , wherein bonding the optical membrane device to the active region substrate comprises solder bonding the optical membrane device to the active region substrate. 
     
     
         4 . A method as claimed in  claim 1 , wherein bonding the optical membrane device to the active region substrate comprises thermocompression bonding the optical membrane device to the active region substrate. 
     
     
         5 . A method as claimed in  claim 1 , wherein a distance between the active region substrate and the membrane device is less than a micrometer. 
     
     
         6 . A method as claimed in  claim 1 , further comprising fabricating the optical membrane device by releasing a membrane structure by partially removing a release layer. 
     
     
         7 . A method as claimed in  claim 6 , wherein the membrane structure is deflected between 1 and 3 μm to tune the VCSEL. 
     
     
         8 . A method as claimed in  claim 1 , further comprising using a spacer device between the active region substrate and the optical membrane device. 
     
     
         9 . A method as claimed in  claim 1 , further comprising controlling a polarization by applying asymmetric stress. 
     
     
         10 . A method as claimed in  claim 1 , wherein the active region substrate includes a multiple quantum well structure. 
     
     
         11 . A method as claimed in  claim 1 , further comprising installing the VCSEL in a package with a thermoelectric cooler. 
     
     
         12 . A method as claimed in  claim 1 , further comprising coupling pump light into the VCSEL with a lens that collimates laser light exiting from the VCSEL. 
     
     
         13 . A method as claimed in  claim 1 , further comprising installing the VCSEL on an optical bench and emitting a swept optical signal that propagates parallel to a top surface of the optical bench. 
     
     
         14 . A method as claimed in  claim 13 , further comprising installing a laser pump on the optical bench for generating pump light for optically pumping. 
     
     
         15 . A method as claimed in  claim 1 , further comprising deflecting an optical membrane of the optical membrane device in a direction away from the active region substrate to tune the VCSEL. 
     
     
         16 . A method as claimed in  claim 1 , further comprising forming a curved mirror structure on the optical membrane device.