Tunable laser modules incorporating micromachined pellicle splitters

Abstract

A micromachined pellicle beam splitter and method of manufacture thereof are disclosed. In one embodiment, the beam splitter includes a silicon frame with a silicon nitride membrane attached to the frame and covering an opening through the frame. Other materials may be utilized, however, the coefficient of thermal expansion (CTE) of the membrane should be greater than that of the frame. The beam splitter may be manufactured by coating a silicon substrate with a layer of silicon nitride, patterning an opposite side of the silicon substrate with a photoresist or a metallic layer to define an opening an etching an opening through the substrate to the silicon nitride with either a dry etch or wet etch technique. An improved tunable laser module incorporating the micromachined pellicle beam splitter and a method of tuning a laser diode are also disclosed.

1 . A method of fabricating a pellicle beam splitter, the method comprising: 
 depositing a silicon nitride film on a first side of silicon substrate,    depositing a mask on a second side of the silicon substrate, the mask defining an opening,    etching the silicon substrate through the opening of the mask to produce an opening in the substrate extending from the second side to the first side thereof and up to the silicon nitride film.    
   
   
       2 . The method of  claim 1  wherein the etching is a wet etch process.  
   
   
       3 . A method of fabricating a pellicle beam splitter, the method comprising: 
 depositing a silicon nitride film on a first side of a first silicon substrate,    depositing a second silicon substrate on the silicon nitride film so that the silicon nitride film is sandwiched between a first side of the second silicon substrate and the first side of the first silicon substrate, 
 depositing masks on second sides of the first and second silicon substrates, the masks each defining openings that are aligned with each other,  
   etching the first and second silicon substrates through the openings of the masks to produce openings in the first and second substrate extending from the second side to the first side of each substrate and up to the silicon nitride film.    
   
   
       4 . The method of  claim 3  wherein the etchings of the first and second silicon substrates are wet etch processes carried out simultaneously and the etching of the first silicon substrate is a wet etch carried out before or after the etching of the second silicon substrate which is a dry etch.