Abstract:
Briefly, in accordance with one or more embodiments, a thermally controlled optical filter comprises a frame coupled to an etalon where the frame includes a resistive thermal device disposed on the frame to obtain thermal measurements of the etalon during operation. The frame may be generally L-shaped or generally square-shaped. The frame may include a fillet that is generally planar, generally beveled or trapezoidal, or generally circular in shape. A heater may be additionally disposed on the frame. The etalon and frame subassembly may be bonded to a micro hot plate that is capable of heating the etalon to an operational temperature.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a Continuation Application of U.S. patent application Ser. No. 13/102,910 filed on May 6, 2011, which is a Divisional of U.S. patent application Ser. No. 12/825,066, filed on Jun. 28, 2010 (now U.S. Pat. No. 7,961,374), which is a Divisional of U.S. patent application Ser. No. 11/731,223 (now U.S. Pat. No. 7,771,071), filed on Mar. 30, 2007. 
     
    
     BACKGROUND 
       [0002]    Thermally controlled optical filters may inadvertently provide thermal cross talk between the temperature of the filter and other sources of temperature variation, for example from the case in which the optical filter is disposed, from the substrate on which the optical filter is mounted, for from another filter disposed proximate to the filter. Furthermore, varying stresses may be imparted on the filter for example via coefficient of thermal expansion (CTE) mismatches and process variations, which may impact the stability of the filter and the reliability of the frequency at which the filter operates to select a desired wavelength of laser light. 
     
    
     
       DESCRIPTION OF THE DRAWING FIGURES 
         [0003]    Claimed subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, such subject matter may be understood by reference to the following detailed description when read with the accompanying drawings in which: 
           [0004]      FIG. 1  is diagram of thermally controlled optical filters in accordance with one or more embodiments; 
           [0005]      FIG. 2  is a diagram of thermally controlled optical filters including a resistive temperature device formed as a generally L-shaped frame in accordance with one or more embodiments; 
           [0006]      FIG. 3  is a diagram of a thermally controlled optical filter including a resistive temperature device formed as a generally L-shaped frame having a generally circular fillet in accordance with one or more embodiments; 
           [0007]      FIG. 4  is a diagram of resistive temperature devices formed in L-shaped frames bonded to an optical filter wafer in accordance with one or more embodiments; and 
           [0008]      FIG. 5  is a diagram of a thermally controlled optical filter including a resistive temperature device formed in a generally square shaped frame in accordance with one or more embodiments. 
       
    
    
       [0009]    It will be appreciated that for simplicity and/or clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements. 
       DETAILED DESCRIPTION 
       [0010]    In the following detailed description, numerous specific details are set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and/or circuits have not been described in detail. 
         [0011]    In the following description and/or claims, the terms coupled and/or connected, along with their derivatives, may be used. In particular embodiments, connected may be used to indicate that two or more elements are in direct physical and/or electrical contact with each other. Coupled may mean that two or more elements are in direct physical and/or electrical contact. However, coupled may also mean that two or more elements may not be in direct contact with each other, but yet may still cooperate and/or interact with each other. Furthermore, the term “and/or” may mean “and”, it may mean “or”, it may mean “exclusive-or”, it may mean “one”, it may mean “some, but not all”, it may mean “neither”, and/or it may mean “both”, although the scope of claimed subject matter is not limited in this respect. 
         [0012]    Referring now to  FIG. 1 , a diagram of thermally controlled optical filters in accordance with one or more embodiments will be discussed. As shown in  FIG. 1 , a thermally controlled optical filter may generally comprise a hot plate type structure, for example a micromachined silicon filter  108  having an optical etalon  112  disposed thereon. Filter  110  may include a resistive temperature device (RTD)  118  and heater  116  that may be utilized to heat etalon  112  to an operational temperature and to take temperature measurements of the temperature of etalon  112  to select and control the temperature of etalon  112 , for example in a feedback arrangement. Etalon  112  may comprise glass or a similar material and may be utilized to filter laser light from a laser (not shown) to tune the laser to a desired operational wavelength. In one or more embodiments, such a laser may comprise, for example, an external cavity laser. Such tuning of the wavelength of laser light passing through etalon  112  may be at least partially accomplished via controlling the temperature of etalon  112 , however the scope of the claimed subject matter is not limited in this respect. 
         [0013]    In one or more embodiments, optical filter  110  may comprise etalon  114  adhered to glass plate  122  which in turn may be adhered to resistive temperature device and heater  118 . Etalon  114  may be adhered to glass plate  122  and/or glass plate  122  may be adhered to micro hot plate  120  having a resistive temperature device  118  and heater  116 , for example using an epoxy or similar type of adhesive, although the scope of the claimed subject matter is not limited in this respect. 
         [0014]    Optical filter  110  may provide thermal isolation as well as mechanical isolation of resistive temperature device  118  and heater  116 . Such an arrangement may generally provide minimal cross-talk between the temperature of filter  110  and any external thermal load, for example case temperature and/or substrate temperature. Optical filter  110  may provide a simpler arrangement for controlling the temperature of etalon  114  resulting in a simpler assembly and manufacturing process. In such an arrangement, any increased cross talk between the temperature of optical filter  110  and the temperature of the case and other filters and/or the sled temperature may be addressed as described herein. Furthermore, any strain on resistive thermal device  118  and heater  116  induced by coefficient of thermal expansion (CTE) type effects and/or processing condition, for example due to relaxation of such strain over time, and any resulting error in temperature measurements, likewise may be addressed as described herein. 
         [0015]    Referring now to  FIG. 2 , a diagram of optically controlled optical filters including a resistive temperature device formed as a generally L-shaped frame in accordance with one or more embodiments will be discussed. As shown in  FIG. 2 , optical filter  210  may be constructed to include resistive thermal device  118  comprising a generally L-shaped frame  212 . Such an L-shaped frame may provide a more precise measurement of the temperature of etalon  114  and further may provide reduced cross talk and/or reduced processing stress on resistive thermal device  118  due to, for example, coefficient of thermal expansion (CTE) mismatch and process type effects. In one or more embodiments, L-shaped frame  212  may comprise a highly thermally conductive material including but not limited to silicon (Si), tungsten copper (WCu), silicon carbide (SiC), and so on. L-shaped frame  212  may be disposed on micro hot plate  120  with heater  116  wherein an electrical connection between resistive thermal device  118  and micro hot plate  120  with heater  116  may be coupled, for example, using solder or wirebond. Such an L-shaped frame  212  for resistive thermal device  118  may be compatible with thin film processes to ad platinum/titanium (Pt/Ti) traces on resistive thermal device  118  in addition to one or more gold pads for solder or wirebond type connections. In one embodiment, L-shaped frame  212  may be arrived at via a dry etched process such as L-shaped frame  212  of optical filter  210 , or alternatively L-shaped frame  212  of optical filter  214  may be arrived at, for example, via a wet etched process of silicon. In one or more embodiments, L-shaped frame  212  may comprise fillet  218  having one or more surfaces disposed at right or nearly right angles, and in one or more alternative embodiments, L-shaped frame  212  may comprise fillet  220  having one or more beveled or trapezoidal type surfaces, although the scope of the claimed subject matter is not limited in these respects. In one or more embodiments, etalon  114  may include an area  216  through which laser light may pass there through proximate to fillet  218  or fillet  220 , although the scope of the claimed subject matter is not limited in these respects. 
         [0016]    Referring now to  FIG. 3 , a diagram of a thermally controlled optical filter including a resistive temperature device from as a generally L-shaped frame having a generally circular fillet in accordance with one or more embodiments will be discussed. As shown in  FIG. 3 , L-shaped frame  212  may comprise a generally circular fillet  310 . In such an embodiment, circular fillet  310  may maximize, or nearly maximize, the contact area between L-shaped frame  212  and etalon  114  while reducing or eliminating clipping of the laser beam passing through area  216  of etalon  114 , although the scope of the claimed subject matter is not limited in this respect. 
         [0017]    Referring now to  FIG. 4 , a diagram of resistive temperature devices formed in L-shaped frames bonded to an optical filter wafer in accordance with one or more embodiments will be discussed. As shown in  FIG. 4 , L-shaped frames  212  may be processed using a standard type micromachined silicon technology or the like. In one or more embodiments, L-shaped frames  212  of resistive thermal devices  118  may be etched and then bonded to a wafer of etalons  114  prior to dicing and then subsequently diced to arrive at optical filter subassemblies. Further as shown in  FIG. 4 , in one embodiment L-shaped frames  212  may be formed via a dry etched wafer  410  or alternatively via a wet etched wafer  114 , although the scope of the claimed subject matter is not limited in these respects. 
         [0018]    Referring now to  FIG. 5 , a diagram of a thermally controlled optical filter including a resistive temperature device formed in a generally square shaped frame in accordance with one or more embodiments will be discussed. As shown in  FIG. 5 , a thermally controlled optical filter may be constructed with a square-shaped frame  510  rather than with an L-shaped frame  212 . In such an arrangement, square-shaped frame  510  may include a circular opening  512  having resistive thermal device  118  disposed along a circumference of circular opening  512 . In one or more embodiments, square-shaped frame  510  may include circular opening  512  having resistive thermal device  118  disposed along a circumference of circular opening  512  and may further include a heater  514  also disposed along a circumference of circular opening  512 . It should be noted that L-shaped frame  212  and square-shaped frame  510  are merely example frames that may include resistive thermal device  118  and/or heater  116 , wherein other shapes of frames likewise may be utilized, and the scope of the claimed subject matter is not limited in these respects. 
         [0019]    Although the claimed subject matter has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and/or scope of claimed subject matter. It is believed that the subject matter pertaining to thermal control of optical filter with local silicon frame and/or many of its attendant utilities will be understood by the forgoing description, and it will be apparent that various changes may be made in the form, construction and/or arrangement of the components thereof without departing from the scope and/or spirit of the claimed subject matter or without sacrificing all of its material advantages, the form herein before described being merely an explanatory embodiment thereof, ad/or further without providing substantial change thereto. It is the intention of the claims to encompass and/or include such changes.