Passive optical resonator with mirror structure suppressing higher order transverse spatial modes

Abstract

An optical resonator is designed to suppress higher order transverse spatial modes. Higher order transverse modes in the inventive optical resonator are forced to be unstable, and ultimately achieving single transverse mode resonator operation. Specifically, the mirror shape or intracavity lens profile is tailored to bound the lower order modes while rendering the higher order modes unstable. This has application in MEMS/MOEMS devices by reducing side mode suppression ratio (SMSR) dependence on alignment tolerances, for example.

1 . A passive optical resonator comprising at least one optical cavity defined by at least two mirror structures in which at least one of the mirror structures has a mirror profile having a diameter and sag that are selected in combination with a length of the cavity to degrade a stability of transverse modes with mode numbers 4 and greater.  
     
     
         2 . A resonator as claimed in  claim 1 , wherein the length of the optical cavity is less than about 50 micrometers, the sag of the mirror profile is less than about 200 nanometers, and a full width at half maximum diameter of the mirror profile is less than 30 micrometers.  
     
     
         3 . A resonator as claimed in  claim 1 , wherein the length of the optical cavity is less than about 30 micrometers, the sag of the mirror profile is less than about 150 nanometers, and a full width at half maximum diameter of the mirror profile is less than 20 micrometers.  
     
     
         4 . A resonator as claimed in  claim 1 , wherein the length of the optical cavity is less than about 20 micrometers, the sag of the mirror profile is less than about 100 nanometers, and a full width at half maximum diameter of the mirror profile is less than 15 micrometers.  
     
     
         5 . A resonator as claimed in  claim 1 , wherein the sag of the mirror profile is less than about 150 nanometers.  
     
     
         6 . A resonator as claimed in  claim 1 , wherein the sag of the mirror profile is less than about 100 nanometers.  
     
     
         7 . A resonator as claimed in  claim 1 , wherein an optical distance between the mirror structures is tunable.  
     
     
         8 . A resonator as claimed in  claim 1 , wherein an optical distance between the mirror structures is tunable by out-of-plane deflection of one of the mirror structures.  
     
     
         9 . An optical resonator comprising at least one optical cavity defined by at least two mirror structures wherein a net profile of the mirror structures is concave in a center region surrounding an optical axis and flat and/or convex in an annular region surrounding the center region, and wherein a diameter of the center regions is selected in response to a mode field diameter of a lowest order mode of the resonator.