Chip-based laser resonator device for highly coherent laser generation

Abstract

A highly-coherent chip-based laser generating system includes a disk resonator incorporating a wedge structure fabricated from a silicon dioxide layer of a chip. The disk resonator is operable to generate a highly-coherent laser from a low-coherence optical pump input provided at an optical power level as low as 60 μW. The disk resonator is fabricated with sub-micron cavity size control that allows generation of a highly-coherent laser using a controllable Stimulated Brillouin Scattering process that includes matching of a cavity free-spectral-range to a Brillouin shift frequency in silica. While providing several advantages due to fabrication on a chip, the highly-coherent laser produced by the disk resonator may feature a Schawlow-Townes noise level as low as 0.06 Hz 2 /Hz (measured with the coherent laser at a power level of about 400 μW) and a technical noise that is at least 30 dB lower than the low-coherence optical pump input.

What is claimed is: 
     
         1 . A method of manufacturing chip-based laser devices for one or more coherent laser generating systems, the method comprising:
 fabricating a batch of disk resonators from a silicon substrate, the fabricating comprising precision control of a diameter dimension to obtain a substantial similar Q factor in each disk resonator.   
     
     
         2 . The method of  claim 1 , wherein the substantial similar Q factor is at least 100 million and as high as 875 million. 
     
     
         3 . The method of  claim 2 , wherein each disk resonator is configurable as to generate a coherent laser that is characterized in part, by a Schawlow-Townes noise level as low as 0.06 Hz 2 /Hz at a power level of about 400 μW. 
     
     
         4 . The method of  claim 3 , wherein the fabricating comprises:
 placing the silicon substrate in a furnace;   introducing steam into the furnace;   raising a temperature inside the furnace to a first temperature level wherein a silicon dioxide layer is formed on a major surface of the silicon substrate;   eliminating a moisture content in the silicon substrate by heating the silicon substrate at a second temperature level in an oxygen-rich environment;   forming a first assembly by applying a photo-resist layer upon a portion of the major surface of the silicon dioxide layer;   immersing the first assembly into a bath containing an etching solution selected for etching silicon dioxide;   forming a second assembly by allowing the etching solution to act upon the silicon dioxide layer of the first assembly for a first period of time that is selected in order to: a) expose a portion of the silicon substrate, and b) form at least one wedge structure in the silicon dioxide layer;   forming a third assembly by extending the first period of time by a second period of time in order to eliminate a foot region formed upon a sloping surface of the at least one wedge structure;   after eliminating the foot region, forming a fourth assembly by removing the photo-resist layer from the third assembly; and   forming at least one waveguide portion from the fourth assembly by exposing the fourth assembly to a xenon difluoride (XeF 2 ) environment that eliminates a portion of the silicon substrate and forms a support pillar below the at least one wedge structure.   
     
     
         5 . The method of  claim 4 , wherein the silicon dioxide layer ranges from about 8 micron thickness to about 10 micron thickness. 
     
     
         6 . The method of  claim 4 , wherein the first period of time is further selected to allow the etching solution to act upon the silicon dioxide layer to form a slope angle ranging from about 7 degrees to about 90 degrees in the sloping surface of the at least one wedge structure. 
     
     
         7 . The method of  claim 6 , wherein an adhesion promoter is incorporated into the photo-resist layer, the adhesion promoter providing an adhesion factor between the photo-resist layer and the silicon dioxide layer, the adhesion factor selected in accordance with the first period of time and the slope angle.