Abstract:
Sound signals are detected. Light signals are generated that pass through a membrane of a bubble within a trench. The sound signals cause deformations within the membrane of the bubble. The light signals are detected after the light signals have passed through the membrane. The sound signals are reconstructed from the light signals detected by the optical detector.

Description:
BACKGROUND  
         [0001]    The present invention concerns transducers and pertains particularly to a fluidic acoustic transducer.  
           [0002]    Acoustic transducers are used to translate sound into electrical signals. In many fields in which transducers are used, such as in the field of communications, it is desirable to shrink the physical size of transducers while maintaining high sensitivity in selected sound ranges.  
         SUMMARY OF THE INVENTION  
         [0003]    In accordance with the preferred embodiment, sound signals are detected. Light signals are generated that pass through a membrane of a bubble within a trench. The sound signals cause deformations within the membrane of the bubble. The light signals are detected after the light signals have passed through the membrane. The sound signals are reconstructed from the light signals detected by the optical detector. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 shows a fluidic acoustic transducer in which sidewall detection is used in accordance with a preferred embodiment of the present invention.  
         [0005]    [0005]FIG. 2 shows a graph of a reflected optical signal as related to heater power in accordance with a preferred embodiment of the present invention.  
         [0006]    [0006]FIG. 3 is a simplified block diagram of circuitry used with an array of transducers in accordance with another preferred embodiment of the present invention.  
         [0007]    [0007]FIG. 4 shows a fluidic acoustic transducer in which bottom up and sidewall detection are used in accordance with another preferred embodiment of the present invention.  
         [0008]    [0008]FIG. 5 shows a fluidic acoustic transducer in which bottom up and side wall detection are used in accordance with another preferred embodiment of the present invention.  
         [0009]    [0009]FIG. 6 shows a fluidic acoustic transducer with acoustic amplification in accordance with another preferred embodiment of the present invention.  
         [0010]    [0010]FIG. 7 shows a fluidic acoustic transducer with acoustic amplification in accordance with another preferred embodiment of the present invention.  
         [0011]    [0011]FIG. 8 shows a fluidic acoustic transducer with acoustic amplification in accordance with another preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 9 shows a fluidic acoustic transducer with acoustic amplification in accordance with another preferred embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    [0013]FIG. 1 shows a fluidic acoustic transducer in which sidewall detection is used. A substrate  11  is, for example, composed of silicon. Alternatively, substrate  11  is another material such as silicon dioxide (SiO2), Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc.  
         [0014]    On top of substrate  11 , a layer  12  of SiO2 material is formed. Within layer  12  of SiO2 material a heater array is formed. The heater array is arranged such that each transducer has either two side heaters or one central heater and two side heaters. Shown in FIG. 1 are side heater  17 , side heater  19  and central heater  18 .  
         [0015]    Layer  12  is a bondable top layer. For example, the top layer is composed of Teos, silica, or fluoropolymers. On top of layer  12 , is placed a planar waveguide that includes cladding  13  within which a core  14  runs. The substrates can be bonded by one of several methods that include anodic bonding, fusion bonding, or soldering. Alternatively, spin on or deposited films (fluoropolymers, teos, etc) can be substituted for a bonded layer.  
         [0016]    A trench  21  is formed, for example, using a wet etch, a dry etch, laser, or photolithographic exposure. Trench  21  is representative of multiple trenches that can be formed on a single substrate, thus allowing formation of multiple acoustic transducers on a single substrate.  
         [0017]    A cap  16  is positioned above trench  21  to form a global plenum  15  used for multiple acoustic transducers. Alternatively, individual caps and heating elements can be put on each trench and be covered by a secondary global cap. Plenum  15  is filled with fluid having an optical index matching that of core  14 .  
         [0018]    Heater  18  is used to form a bubble  20 . Side heater  17  and side heater  19  are used to keep sidewalls of trench  21  dry. A laser signal  23  traveling through core  14  is either fully reflected by bubble  20 , fully transmitted through fluid within trench  21 , or partially transmitted and partially reflected by a combination of bubble  20  and fluid within trench  21 , depending on the size of bubble  20 .  
         [0019]    Within the operating range of the transducer, a membrane  24  of bubble  20  is, at least partially, within the area of trench  21  that laser signal  23  enters. Sound waves  22  traveling through cap  16  and fluid within global plenum  15  impinge membrane  24  and deform it. The resulting patterns within membrane  24  are picked up by the portion of laser  23  that transmits through trench  21 . The resulting optical signal is detected and sound signals are extracted. The size and shape of trench  21  as well as the temperature and pressure of liquid and vapor within trench  21  are controlled to “tune” the optical signal generated by laser signal  23  traveling through trench  21  so that the resulting extracted sound signals have excellent response within desired sound frequencies. An array of transducer, each with its own customized trench and optical signal, can be used to ensure excellent response over a sound frequency spectrum.  
         [0020]    [0020]FIG. 2 shows a graph of reflected optical signal as related to heater power. A vertical axis  111  represents the percentage of optical signal  23  (shown in FIG. 1) that is reflected as it travels through trench  21 . A horizontal axis  112  represents power through resistor  18 . A trace  113  represents power-up response. A trace  114  represents power-down response. An operating range  115  indicates where the percentage of optical signal  23  (shown in FIG. 1) that is reflected as it travels through trench  21  turn-on power is between 0% to 100%.  
         [0021]    [0021]FIG. 3 is a simplified block diagram of circuitry used with an array of transducers  100 . Fluid pressure control  104  controls fluid pressure within one or more global plenums used to stored fluid for the array of transducers  100 . Temperature control  105  controls power placed through heaters within array of transducers  100 . The heaters control the size of bubbles within the transducers.  
         [0022]    Optical fibers  101  carry laser signals to array of transducers  100 . Optical fibers  102  carry any unreflected light that passes through array of transducers  100 . Optical detectors  103  detect light signals carried by optical fibers  102 . Any sound signals encoded within the light signals detected by optical detectors  103  are extracted by filters located within optical detectors  103  or in additional electrical circuitry.  
         [0023]    [0023]FIG. 4 shows a fluidic acoustic transducer in which bottom up and sidewall detection, is used. A substrate  30  is, for example, composed of silicon. Alternatively, substrate  30  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. Resistors  31  produce heat. The inner track of each of resistors  31  has no metal covering so that the area between resistors  31  is hot as if there was a third resistor. At least the portion of substrate  30  below a trench  41  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  30  or by using materials such as silicon or quartz that will be very transmissive to IR signals. If needed, an optional central resistor  331  can be formed from an IR transmissive film such as polysilicon, IRSiO2, WSIN, or TaSiN. Over resistors  31  is placed a dielectric coating  332  transmissive to IR, such as Si3N4 or SiO2. Regions  32  are filled with liquid. Pillars  37  are used for side wall heat conduction. Alternatively, a high quality pyrolytic IR transmissive film such as sputtered silicon can be used as a mesa for conduction of heat.  
         [0024]    A planar waveguide that includes cladding  33  within which a core  34  runs. The substrates can be bonded by one of several methods that include anodic bonding, fusion bonding, or soldering. Alternatively, spin on or deposited films (fluoropolymers, teos, etc) can be substituted for a bonded layer.  
         [0025]    A cap  36  is positioned above trench  41  to form a global plenum  35  for multiple acoustic transducers. Alternatively, individual caps and heating elements can be put on each trench and be covered by a secondary global cap. Plenum  35  is filled with fluid having an optical index matching that of core  34 . Resistor  31  and pillars  37  are used to form a bubble  40 . Note dielectric coating  332  is thinned or etched below bubble  40  to increase heating there and to force bubble  40  to see the middle hotter than the edges. A laser signal  43  traveling through core  34  is either fully reflected by bubble  40 , fully transmitted through fluid within trench  41 , or partially transmitted partially reflected by a combination of bubble  40  and fluid within trench  41 , depending on the size of bubble  40 . For example, cap  36  is composed of Si3N4.  
         [0026]    Within the operating range of the transducer, a membrane  46  of bubble  40  is, at least partially, within the area of trench  41  that laser signal  43  enters. Sound waves traveling through cap  36  and fluid within global plenum  35  impinge membrane  46  and deform it. The resulting patterns within membrane  46  are picked up by the portion of laser  43  that transmits through trench  41 . The resulting optical signal is detected and sound signals are extracted.  
         [0027]    A reflector  38  is located on the bottom of cap  36 . For example, reflector  38  is composed of reflective material such as aluminum (Al) or gold (Au). A laser source  42  produces a laser signal  38  that is reflected by a reflecting surface  44 , travels through trench  41 , is reflected by reflector  38 , and is detected by a receiver  45 . For example, Laser signal is an IR signal or a Near Infrared Signal (NIR) signal. As laser signal  39  travels across membrane  46 , the vibrating patterns within membrane  46  are picked up by laser signal  39  and can be extracted from the optical signal detected by receiver  45 .  
         [0028]    Provided sound waves are detected and extracted sufficient for a particular application using laser signal  39  and receiver  45 , then laser signal  43  and the planar waveguide that includes cladding  33  and core  34  can be omitted.  
         [0029]    Laser source  42  and a receiver  45 , may be implemented as an external laser source and receiver. Alternatively, laser source  42  and a receiver  45  are replaced by a bonded chip that includes an integrated vertical cavity surface emitting laser (VCSEL) and photodetector.  
         [0030]    [0030]FIG. 5 shows another embodiment of a fluidic acoustic transducer in which bottom up detection is used. A substrate  50  is, for example, composed of silicon. Alternatively, substrate  50  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. Resistors  51  produce heat. The inner track of each of resistors  51  has no metal covering so that the area between resistors  51  is hot as if there was a third resistor. At least the portion of substrate  50  below a trench  61  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  50  or by using materials such as silicon or quartz that are transmissive of IR signals. If needed, an optional central resistor  351  can be formed from an IR transmissive film such as polysilicon, IRSiO2, WSIN, or TaSiN. Over resistors  51  is placed a dielectric coating  352  transmissive to IR, such as Si3N4 or SiO2. Regions  52  are filled with liquid. Pillars  57  are used for side wall heat conduction. Alternatively, a high quality pyrolytic IR transmissive film such as sputtered silicon can be used as a mesa for conduction of heat.  
         [0031]    A planar waveguide includes cladding  53  and a core  54 . The substrates can be bonded by one of several methods that include anodic bonding, fusion bonding, or soldering, spin on materials, or deposition and planarization.  
         [0032]    An IR transmissive layer  67  is placed over core layer  54 . For example, IR transmissive layer  67  is composed of quartz. Transmissive layer  67  includes a hollow area  68  extending over trench  61 . Fluid having an optical index matching that of core  54  is stored in trench  61  and hollow area  68 .  
         [0033]    A layer  55 , composed of, for example, index matching fluid is positioned above IR transmissive layer  67 . An external seal  56  is positioned over layer  55 . For example, external seal  56  is composed of Si3N4.  
         [0034]    Resistors  51  and pillars  57  are used to form a bubble  60 . A laser signal  63  traveling through core  54  is either fully reflected by bubble  60 , fully transmitted through fluid within trench  61 , or partially transmitted partially reflected by a combination of bubble  60  and fluid within trench  61 , depending on the size of bubble  60 . Within the operating range of the transducer, a membrane  66  of bubble  60  is, at least partially, within the area of trench  61  that laser signal  63  enters.  
         [0035]    A reflector  58  is located on the bottom of external seal  56 . For example, reflector  58  is composed of a reflective material stack such as Au and titanium (Ti), Au and Ta, or aluminum (Al). A laser source  62  produces a laser signal  59  that is reflected by a reflecting surface  64 , travels through trench  61 , is reflected by reflector  58 , and is detected by a receiver  65 . For example, Laser signal  59  is an IR signal or an NIR signal. As laser signal  59  travels across membrane  66 , the vibrating patterns within membrane  66  are picked up by laser signal  59  and can be extracted from the optical signal detected by receiver  65 .  
         [0036]    Provided sound waves detected and extracted are sufficient for a particular application using laser signal  59  and receiver  65 , then laser signal  63  and the planar waveguide that includes cladding  53  and core  54  can be omitted.  
         [0037]    [0037]FIG. 6 shows a fluidic acoustic transducer with acoustic amplification in accordance with another preferred embodiment of the present invention. A substrate  70  is, for example, composed of silicon. Alternatively, substrate  70  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. Resistors  71  produce heat. The inner track of each of resistors  71  has no metal covering so that the area between resistors  71  is hot as if there was a third resistor. At least the portion of substrate  70  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  70 . If needed, an optional central resistor  88  can be formed from an IR transmissive film such as polysilicon, IRSiO2, WSIN, or TaSiN. Over resistors  71  is placed a dielectric coating  87  transmissive to IR, such as Si3N4 or SiO2. Regions  72  are filled with liquid. Pillars  77  are used for side wall heat conduction. Alternatively, a high quality pyrolytic IR transmissive film such as sputtered silicon can be used as a mesa for conduction of heat.  
         [0038]    A layer  74 , composed of, for example, index matched fluid, is positioned above glass layer  73 . An external seal  75  is positioned over layer  74 . For example, external seal  75  is composed of Si3N4.  
         [0039]    Resistors  71  and pillars  77  are used to form a bubble  80 . A reflector  78  is located on the bottom of external seal  75 . For example, reflector  78  is composed of a reflective material stack such as Au and Ti, Au and Ta, or Al. A laser source  82  produces a laser signal  79  that is reflected by a reflecting surface  84 , travels through bubble  80 , is reflected by reflector  78 , and is detected by a receiver  85 . For example, laser signal  79  is an IR signal or an NIR signal. As laser signal  79  travels across membrane  86 , the vibrating patterns within membrane  86  are picked up by laser signal  79  and can be extracted from the optical signal detected by receiver  85 .  
         [0040]    [0040]FIG. 7 shows a fluidic acoustic transducer with acoustic amplification and differential electrical comparison. A substrate  130  is, for example, composed of silicon. Alternatively, substrate  130  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. Resistors  131  produce heat. The inner track of each of resistors  131  has no metal covering so that the area between resistors  131  is hot as if there was a third resistor. At least the portion of substrate  130  below a trench  141  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  130 . If needed, an optional central resistor  150  can be made from an IR transmissive film such as polysilicon, IRSiO2, WSIN, or TaSiN. Over resistors  131  is placed a dielectric coating  151  transmissive to IR, such as Si3N4 or SiO2. Regions  132  are filled with liquid. Pillars  137  are used for side wall heat conduction. Alternatively, a high quality pyrolytic IR transmissive film such as sputtered silicon can be used as a mesa for conduction of heat. A planar waveguide that includes cladding  133  within which a core  134  runs. The substrates can be bonded by one of several methods that include anodic bonding, fusion bonding, soldering, spin on polymers (fluoropolymers or Teos based) or deposited and planarized materials.  
         [0041]    A chamber  148  and a chamber  147  are formed, for example, from two bonded Silicon or SiC wafers. Chamber  148  and chamber  147  are filled with liquid such as cyclohexane, 2-fluorotuolene, or benzene. A boundary layer  135  and a boundary layer  136  are composed of, for example, of a 5000 Angstrom thick layer of Si3N4. A section  149  is composed of, for example, boron doped silicon or polysilicon, or a piezoelectric ZnO transducer. An IR reflective region  138  is composed of, for example, Al or Au. Chamber  148  functions as a resonance chamber.  
         [0042]    Resistors  131  and pillars  137  are used to form a bubble  140 . A laser source  142  produces a laser signal  139  that is reflected by a reflecting surface  144 , travels through trench  141 , is reflected by reflective region  138 , and is detected by a receiver  145 . For example, Laser signal is an IR signal or an NIR signal. As laser signal  139  travels across membrane  146 , the vibrating patterns within membrane  146  are picked up by laser signal  139  and can be extracted from the optical signal detected by receiver  145 .  
         [0043]    [0043]FIG. 8 shows a fluidic acoustic transducer with acoustic amplification and differential electrical comparison. A substrate  170  is, for example, composed of silicon. Alternatively, substrate  170  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. Resistors  171  produce heat. The inner track of each of resistors  171  has no metal covering so that the area between resistors  171  is hot as if there was a third resistor. At least the portion of substrate  170  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  170 . If needed, an optional central resistor  371  can be made from an IR transmissive film such as polysilicon, IRSiO2, WSIN, or TaSiN. Over resistors  171  is placed a dielectric coating  372  transmissive to IR, such as Si3N4 or SiO2. Regions  172  are filled with liquid. Pillars  177  are used for side wall heat conduction. Alternatively, a high quality pyrolytic IR transmissive film such as sputtered silicon can be used as a mesa for conduction of heat.  
         [0044]    A chamber  188  and a chamber  187  are formed, for example, from two bonded Silicon or SiC wafers. Chamber  188  and chamber  187  are filled with liquid such as cyclohexane, 2-fluorotuolene, or benzene. A boundary layer  175  and a boundary layer  176  are composed of, for example, of a 5000 Angstrom thick layer of Si3N4. A section  189  is composed of, for example, boron doped silicon or polysilicon, or a piezo ZnO transducer. An IR reflective region  178  is composed of, for example, Al or Au. Chamber  188  functions as a resonance chamber.  
         [0045]    Resistors  171  and pillars  177  are used to form a bubble  180 . A laser source  182  produces a laser signal  179  that is reflected by a reflecting surface  184 , travels through bubble  180 , is reflected by reflection region  178 , and is detected by a receiver  185 . For example, laser signal  179  is an IR signal or an NIR signal. As laser signal  179  travels across membrane  186 , the vibrating patterns within membrane  186  are picked up by laser signal  179  and can be extracted from the optical signal detected by receiver  185 .  
         [0046]    [0046]FIG. 9 shows a fluidic acoustic transducer with acoustic amplification and differential electrical comparison. A substrate  230  is, for example, composed of silicon. Alternatively, substrate  230  is another material such as SiO2, Si3N4, SiC, silicon on sapphire (SOS), silicon on insulator (SOI), silicon on another type of material, quartz, etc. At least the portion of substrate  230  needs to be transmissive of infrared (IR) signals. This is done, for example by placing a window within substrate  230 . Regions  232  are filled with liquid. A planar waveguide that includes cladding  233  within which a core  234  runs. The substrates can be bonded by one of several methods that include anodic bonding, fusion bonding, soldering, spin on polymers (fluoropolymers or Teos based) or deposited and planarized materials.  
         [0047]    A chamber  248  and a chamber  247  are formed, for example, from two bonded Silicon or SiC wafers. Chamber  248  is filled with liquid such as cyclohexane, 2-fluorotuolene, or benzene. Chamber  247  is filled, for example, with an acoustic gel packed for matching density of chamber  248 . Alternatively, chamber  247  is open and exposed to the surrounding environment. A boundary layer  236  is composed of, for example, of a 5000 Angstrom thick layer of Si3N4. A section  249  is composed of, for example, boron doped silicon or polysilicon, or a piezo ZnO transducer. An IR reflective region  238  is composed of, for example, Al or Au. Chamber  248  functions as a resonance chamber.  
         [0048]    A heater  250 , a heater  251  and a heater  252  are used to form a bubble  240 . Optional heaters  231 , dielectric coating  253  and optional pillars  237  can be used to provide sidewall heat and heat conduction. A laser source  242  produces a laser signal  239  that is reflected by a reflecting surface  244 , travels through bubble  240 , is reflected by reflective region  238 , and is detected by a receiver  245 . For example, Laser signal is an IR signal or an NIR signal. As laser signal  239  travels across membrane  246 , the vibrating patterns within membrane  246  are picked up by laser signal  239  and can be extracted from the optical signal detected by receiver  245 .  
         [0049]    The foregoing discussion discloses and describes merely exemplary methods and embodiments of the present invention. As will be understood by those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.