Abstract:
A micro-etalon having non-beveled outer edges may be mass-produced without suffering from expected breakage problems. Such a configuration allows etalons to be mass-produced, i.e., on a wafer level. The mass-production preferably includes aligning spacer block strips to be diced with two reflective surfaces to form the etalon.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to etalons, such as Fabry-Perot etalons, and associated methods, more particularly to straight-edged etalons and methods of mass-producing etalons. 
     2. Description of Related Art 
     An example of a conventional rectangular etalon  10  is shown in FIGS. 1A and 1B. The etalon  10  includes two plane, parallel, highly reflective surfaces  12  on plates  14 . The surfaces  12  are separated by spacer blocks  16 , forming a gap  19  there between. The gap  19  can be an air-filled gap, a gas-filled gap, or a vacuum. 
     As can be seen therein, edges  18  of all components of the etalon  10  are beveled. This beveling is used to insure durability of the etalon while it is being integrated into a system, particularly for preventing chips on the etalon. However, this beveling does not lend itself to mass production of etalons. 
     Conventionally, etalons have been larger than on a micro scale and a large number of etalons were not required for a system. However, the use of etalons in communications systems, particularly with wavelength division multiplexed systems, has become more widespread. The use of etalons in communication systems is taught, for example, in U.S. Pat. No. 4,813,756 entitled “Etalon Filters for Optical Channel Selection in Wavelength Division Multiplexed Fiber Systems” and U.S. Pat. No. 5,646,762 entitled “Optical Communication System Using Tandem Fabry-Perot Etalon for Wavelength Selection,” both of which are herein incorporated by reference in their entirety. 
     Such applications require both small etalons and a large number of etalons. The beveling of the conventional etalons makes both the small size and the mass production of such etalons impractical. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore directed to a micro-etalon and a method of mass producing such micro-etalons which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art. 
     It is an object of the present invention to create a micro-etalon which may be mass-produced. 
     These and other objects may be realized by providing an etalon including a first plate having a first reflective surface, a second plate having a second reflective surface, said second reflective surface facing said first reflective surface, and spacer blocks between the first and second reflective surfaces which separate the first and second reflective surfaces, outer edges of the first plate, the second plate and the spacer blocks being non-beveled. 
     The outer edges may all be straight. All dimensions of the etalon may be under 10 mm. The first plate, the second plate and the spacer blocks may all have been cut from wafers. The cross-sections of the etalon may be rectangular. The outer edges of the spacer blocks may be aligned with outer edges of the plates. 
     It is a further object of the present invention to provide a method of mass-producing micro-etalons. 
     These and other objects may be realized by providing a method of producing a plurality of etalons including slitting a spacer substrate into spacer strips, aligning spacer strips on a first plate substrate having a first reflective surface facing the spacer strips, aligning a second plate substrate to the first plate substrate with the spacer strips aligned thereon, the second plate substrate having a second reflective surface facing the spacer strips, and dicing aligned first plate substrate, spacer strips, and second plate substrate to form the plurality of etalons. 
     Before dicing to form the plurality of etalons, spacer strips may be fixed to the first and second wafer substrates. The spacer substrate, the first plate substrate and the second plate substrate may all have the same surface dimensions prior to slitting and dicing. The aligning of the spacer strips to the first plate substrate may include aligning the slit spacer substrate strips to the first plate substrate, having removed undesired spacer strips. The substrates may be wafers of any shape. 
     These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, aspects and advantages will be described with reference to the drawings, in which: 
     FIG. 1A is a front view of a conventional rectangular etalon; 
     FIG. 1B is a side view of the conventional rectangular etalon of FIG. 1A; 
     FIG. 2A is a front view of an etalon in accordance with the present invention; 
     FIG. 2B is a side view of the etalon of the present invention of FIG. 2A; 
     FIG. 2C is a sectional view taken along the lines I—I of FIG. 2A; 
     FIG. 3 is a flow chart for a method of creating etalons in accordance with the present invention; and 
     FIG. 4 is an illustration of the spacer strips placed upon a substrate in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 2A-2C illustrate an etalon  20  in accordance with the present invention. The etalon  20  includes a pair of plane, parallel, reflecting surfaces  22  on plates  24  separated by spacer blocks  26 . A gap  29  between the reflecting surfaces  22  formed by the spacer blocks  26  can be filled with air, gas, or be evacuated. The view of FIG. 2C, taken along lines I—I of FIG. 2A more clearly illustrates the reflecting surface  22  which is typically coated with materials having the desired reflection properties. 
     Thus, the etalon  20  has non-beveled edges on all exterior surfaces, while having spacer blocks  26  on outside edges thereof for mechanical stability. Preferably, all the edges are straight and all cross-sections of the etalons are rectangular. Preferably, the spacer blocks  26  are made of low expansion glass for thermal stability. Spacer block size is minimized to offer maximum aperture while retaining mechanical rigidity. 
     In contrast to the etalon  10 , the etalon  20  in accordance with the present invention has straight edges, i.e., outer edges which are not beveled. In creating the smaller etalons required for recent applications, e.g., telecommunications, the present invention exploits the fact that etalons below a certain size, e.g., on the order of 10 mm×10 mm×10 mm or less, are no longer subject to the same mechanical problems which required the beveled edges of the previous etalons. Additionally, elimination of the beveling allows even further reduction of the size of the etalons. Finally, the elimination of the bevels allows the etalons to be mass-produced, as discussed below. 
     FIG. 3 is a flow chart illustrating a method of mass-producing etalons in accordance with the present invention. As long as bevels were believed to be required, such mass-production was impractical, as there was no way to bevel the edges of the etalon in a mass fashion. 
     In step  40 , a wafer or substrate of material to be used as the spacer blocks is slit into long strips. In step  42 , these strips are aligned and fixed to a wafer or substrate of material, including the reflective surface, to serve as one of the plates. These strips are spaced apart by a desired width of the gap  29 . For ease of alignment, preferably the spacer wafer is the same surface size as the plate wafer, i.e., the thickness may vary, but the outside dimensions are the same. Then, the appropriate spacer strips may be fixed to the plate. 
     In step  44 , another plate wafer or substrate is aligned and fixed on top of the plate wafer with the attached spacer strips, and with the second wafer&#39;s reflecting surface facing the plate wafer with the attached spacer strips. In step  46 , the resultant structure is diced, thereby creating the straight-edged micro-etalon. 
     FIG. 4 illustrates a top view of a circular plate wafer  50  with a reflective surface  58  on a top surface thereof and with spacer strips  52  placed on the top surface spaced by a desired air gap width. The dashed lines  54  indicate an example of horizontal dicing lines and dashed lines  56  indicate an example of vertical dicing lines set in accordance with a desired size of the etalon  20 . The plate wafer pair with the spacer strips interposed there between will be diced along these lines to form an etalon  20  of the desired size. While the substrates in FIG. 4 are illustrated as circular wafers, substrates of other shapes, such as rectangles, may be employed. Conventional processing equipment is better able to handle the conventional circular wafer. 
     Thus, the etalon in accordance with the present invention has non-beveled outer edges, while having intra cavity spacer blocks adjacent to the outside edges thereof for mechanical stability. Preferably, all the edges are straight and all cross-sections of the etalons are rectangular. Such etalons may be mass-produced using wafers and dicing. 
     While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the present invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility without undue experimentation. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.