Laser device, a light signal generation device, and an optical resonator and a method for producing light

Abstract

A laser device includes a ridge waveguide having an active layer between upper and lower cladding layers. A ridge formed in the upper cladding layer defines the width of a light guiding region in the active layer, and is formed so that a portion of the light guiding region extends into the ridge. A plurality of reflecting slots extend across and into the ridge to a depth sufficient to extend into the extending portion in order that the reflectivity of each slot is on the order of 2%. The slots intersect more than 20% of the total mode energy in the light guiding region, and this in combination with the gain of the active layer facilitates lasing within the light guiding region independently of the reflectivity of end facets of the waveguide. The laser device is particularly suitable for integrally forming with other optical components on a single semiconductor chip.

1 . A laser device comprising a waveguide, a longitudinally extending light guiding region defined within the waveguide, at least two reflecting means at locations spaced apart longitudinally relative to the light guiding region and at least one of the reflecting means being located intermediate longitudinally spaced apart ends of the waveguide for partially reflecting light being guided in the light guiding region, the amplitude of the reflectivity of each reflecting means being at least 2%, and the amplitude of the combined reflectivity of the respective reflecting means is such that lasing is independent of the reflectivity of at least one of any facets in which the light guiding region may terminate. 
     
     
         2 . A laser device as claimed in  claim 1  in which at least two reflecting means are provided intermediate the longitudinally spaced apart ends of the waveguide, and the amplitude of the combined reflectivity of the respective reflecting means is such that lasing is independent of the reflectivity of any of the facets in which the light guiding region terminates, and preferably, the reflecting means are located intermediate the opposite longitudinally spaced apart ends of the light guiding region, and preferably, the reflecting means are located in the waveguide, and advantageously, the amplitude of reflectivity of each reflecting means lies in the range of 2% to 20%, and preferably, the amplitude of the reflectivity of each reflecting means lies in the range of 5% to 15%, and advantageously, the amplitude of the reflectivity of each reflecting means is approximately 10%, and preferably, each reflecting means extends into the light guiding region, and advantageously, the light guiding region comprises an active region, and each reflecting means extends into the light guiding region to a location spaced apart from the active region, and preferably, at least four reflecting means are provided, and preferably, at least six reflecting means are provided, and advantageously, the outer two of the reflecting means define a volume in the light guiding region in which lasing occurs. 
     
     
         3 . A laser device as claimed in  claim 1  in which each reflecting means comprises a refractive index altering means for altering the refractive index of the light guiding region adjacent the location of the refractive index altering means, and preferably, each reflecting means is formed by a slot located in the waveguide for providing the partial reflection of the light in the light guiding region adjacent the slot, and advantageously, each reflecting slot extends substantially laterally of the light guiding region, and preferably, at least some of the reflecting slots are at least partially filled with a reflecting medium, and preferably, the reflecting medium is a metal material, and advantageously, the waveguide is provided by a ridge waveguide having an elongated ridge extending longitudinally along the waveguide, the ridge defining the light guiding region, and preferably, each reflecting means is located in the ridge, and advantageously, each reflecting means extends into the ridge to a depth substantially similar to the depth of the ridge, and preferably, the light guiding region extends into the ridge. 
     
     
         4 . A laser device as claimed in  claim 1  in which the waveguide comprises an active layer located between an upper cladding layer and a lower cladding layer, the active layer forming the active region, and preferably, the ridge is formed in the upper cladding layer and defines the lateral width of the light guiding region in the active layer, and advantageously, each reflecting means extends into a portion of the light guiding region defined in the upper cladding layer, and terminates at a location therein spaced apart from the active layer, and preferably, the waveguide is in the form of an optical resonator. 
     
     
         5 . A laser device as claimed in  claim 1  in which the laser device is a tuneable laser device, and the light guiding region defines a first light guiding region and a second light guiding region communicating with the first light guiding region, at least two of the reflecting means being at locations spaced apart longitudinally relative to the first light guiding region to produce a first mirror loss spectrum associated with the first light guiding region with minimum peak values at respective first wavelength values, at least two of the reflecting means at locations spaced apart longitudinally relative to the second light guiding region to produce a second mirror loss spectrum associated with the second light guiding region with minimum peak values at respective second wavelength values, and a refractive index varying means for selectively varying the refractive index of at least the first light guiding region for in turn varying the first mirror loss spectrum until one of the first wavelength values is similar to one of the second wavelength values to produce light of a selected wavelength. 
     
     
         6 . A laser device as claimed in  claim 5  in which the refractive index varying means comprises a means for injecting a first electrical current into the first light guiding region for altering the refractive index thereof, and preferably, a means is provided for varying the first current for in turn varying the refractive index of the first light guiding region, and advantageously, the refractive index varying means comprises a means for injecting a second electrical current into the second light guiding region for varying the refractive index thereof, and preferably, a means is provided for varying the second current for in turn varying the refractive index of the second light guiding region. 
     
     
         7 . A laser device as claimed in  claim 5  in which the means for injecting the first and second currents are operable independently of each other for independently varying the refractive indices of the respective first and second light guiding regions, and preferably, an electrical isolating means is provided for electrically isolating the first and second light guiding regions from each other, and advantageously, the light guiding region defines a third light guiding region intermediate the first and second light guiding regions and communicating therewith, the active region extending in the third light guiding region, and the third light guiding region being adapted to be pumped with an electrical current for generating light therein, and preferably, respective electrical isolating means are provided for substantially electrically isolating the third light guiding region from the respective first and second light guiding regions, and advantageously, the active region extends into the first and second light guiding regions, and the first and second light guiding regions are adapted to be pumped with an electrical current, and preferably, the waveguide is a semiconductor laser, and preferably, the waveguide comprises a laser diode for producing light, and advantageously, the waveguide is adapted for receiving a pumping current. 
     
     
         8 . A light signal generating device comprising a waveguide defining a laser device as claimed in  claim 1  for producing light, and an optical component integrally formed with the laser device, a light guiding region being defined in the waveguide, which forms the light guiding region of the laser device and a light guiding region of the optical component, and preferably, the waveguide comprises an active region located between an upper cladding layer and a lower cladding layer, the active region forming the light guiding region of the laser device and the optical component, and a longitudinally extending ridge being formed in the upper cladding layer defining the lateral width of the light guiding region of at least the laser device, and preferably, the ridge defines the lateral width of the light guiding region of the optical component, and advantageously, an electrical isolating means is provided for substantially electrically isolating the laser device from the optical component, and preferably, the electrical isolating means is formed by an isolating slot extending into the ridge intermediate the laser device and the optical component, and advantageously, the laser device and the optical component are integrally formed in a single piece of material, and preferably, the laser device and the optical component are integrally formed in a single piece of semiconductor material, and advantageously, the optical component is selected from one or more of the following:
 an optical modulator, 
 an optical sensor, 
 an optical detector, 
 an optical amplifier, 
 an optical splitter, 
 an optical interferometer and 
 an optical multiplexer. 
 
     
     
         9 . A light signal generating device comprising an elongated waveguide formed on a single piece of semiconductor material, an elongated longitudinally extending light guiding region being defined in the waveguide, the light guiding region defining a first light guiding region of a light generating device and a second light guiding region of an optical component, the second light guiding region communication with the first light guiding region for receiving light generated therein, at least two reflecting means at locations spaced apart longitudinally relative to the first light guiding region and at least one of the reflecting means being located intermediate longitudinally spaced apart ends of the waveguide for partially reflecting light in the first light guiding region, the amplitude of the reflectivity of each reflecting means being at least 2%, and the amplitude of the combined reflectivity of the respective reflecting means being such that lasing is independent of the reflectivity of at least one of any facets in which the light guiding region may terminate. 
     
     
         10 . A light signal generating device as claimed in  claim 9  in which at least two reflecting means are provided intermediate the longitudinally spaced apart ends of the waveguide, and the amplitude of the combined reflectivity of the respective reflecting means is such that lasing in the first light guiding region is independent of the reflectivity of any of the facets in which the light guiding region may terminate, and preferably, the respective reflecting means are located in the waveguide adjacent the first light guiding region, and preferably, the amplitude of the reflectivity of each reflecting means lies in the range of 2% to 20%, and advantageously, the amplitude of the reflectivity of each reflecting means lies in the range of 5% to 15%, and preferably, the amplitude of the reflectivity of each reflecting means is approximately 10%, and advantageously, each reflecting means extends into the first light guiding region, and preferably, the light guiding region comprises an active region, and each reflecting means extends into the first light guiding region to a location spaced apart from the active region, and advantageously, at least four reflecting means are provided, and preferably, the outer two of the reflecting means define a volume in the first light guiding region in which lasing occurs. 
     
     
         11 . A light signal generating device as claimed in  claim 9  in which each reflecting means is formed by a slot located in the waveguide for providing the partial reflection of the light in the light guiding region adjacent the slot, and preferably, each reflecting slot extends substantially laterally of the light guiding region, and advantageously, at least some of the reflecting slots are at least partially filled with a reflecting medium, and preferably, the waveguide is provided by a ridge waveguide having an elongated ridge extending longitudinally along the waveguide, the ridge defining the light guiding region, and preferably, each reflection causing means is located in the ridge, and advantageously, the waveguide comprises an active layer located between an upper cladding layer and a lower cladding layer, the active layer forming the active region, and preferably, the ridge is formed in the upper cladding layer and defines the lateral width of the wave guiding region in the active layer, and each reflecting means extends into a portion of the light guiding region defined in the upper cladding layer, and terminates at a location therein spaced apart from the active layer, and advantageously, the optical component is selected from one or more of the following:
 an optical modulator, 
 an optical sensor, 
 an optical detector, 
 an optical amplifier, 
 an optical splitter, 
 an optical interferometer and 
 an optical multiplexer. 
 
     
     
         12 . A light signal generating device as claimed in  claim 9  in which the optical component is an optical modulator, and the waveguide adjacent the second light guiding region is adapted for receiving a control voltage signal for modulating light, and preferably, the optical component is an optical detector, and the waveguide adjacent the second light guiding region is adapted for producing an emf across the second light guiding region in response to detecting light, and advantageously, an electrical isolating means for substantially electrically isolating the first light guiding region and the second light guiding region from each other is provided, and preferably, the waveguide adjacent the first light guiding region defines a laser diode for producing the light, and preferably, the first and second light guiding regions defined in the waveguide are integrally formed on a semiconductor chip. 
     
     
         13 . An optical resonator comprising a waveguide, a longitudinally extending light guiding region defined within the waveguide, at least two reflecting means at locations spaced apart longitudinally relative to the light guiding region and at least one of the reflecting means being located intermediate longitudinally spaced apart ends of the waveguide for partially reflecting light being guided in the light guiding region, the amplitude of the reflectivity of each reflecting means being at least 2%, and the amplitude of the combined reflectivity of the respective reflecting means being such that lasing is independent of the reflectivity of at least one of any facets in which the light guiding region may terminate. 
     
     
         14 . An optical resonator as claimed in  claim 13  in which at least two reflecting means are provided intermediate the longitudinally spaced apart end of the waveguide, and the amplitude of the combined reflectivity of the respective reflecting means is such that lasing is independent of the reflectivity of any of the facets in which the light guiding region terminates, and preferably, the amplitude of the reflectivity of each reflecting means lies in the range of 2% to 20%, and preferably, the amplitude of the reflectivity of each reflecting means lies in the range of 5% to 15%, and advantageously, the amplitude of the reflectivity of each reflecting means is approximately 10%, and preferably, each reflecting means extends into the light guiding region, and preferably, the light guiding region comprises an active region, and each reflecting means extends into the light guiding region to a location spaced apart from the active region, and advantageously, the outer two of the reflecting means define a volume in the light guiding region in which lasing occurs. 
     
     
         15 . An optical resonator as claimed in  claim 13  in which each reflecting means is formed by a slot located in the waveguide for providing the partial reflection of the light in the light guiding region adjacent the slot, and preferably, each reflecting slot extends substantially laterally of the light guiding region, and advantageously, at least some of the reflecting slots are at least partially filled with a reflecting medium, and preferably, the waveguide is provided by a ridge waveguide having an elongated ridge extending longitudinally along the waveguide, the ridge defining the light guiding region, and each reflection causing means is located in the ridge. 
     
     
         16 . A method for producing light in a waveguide of the type having a longitudinally extending light guiding region defined therein, the method comprising providing at least two reflecting means at locations spaced apart longitudinally relative to the light guiding region, and at least one of the reflecting means is located intermediate longitudinally spaced apart ends of the waveguide for partially reflecting light being guided in the light guiding region, the amplitude of the reflectivity of each reflecting means being at least 2%, and the amplitude of the combined reflectivity of the respective reflecting means being such that lasing is independent of the reflectivity of at least one of any facet in which the light guiding region may terminate. 
     
     
         17 . A method as claimed in  claim 16  in which at least two reflecting means are provided intermediate the longitudinally spaced apart ends of the waveguide, and the amplitude of the combined reflectivity of the respective reflecting means is such that lasing is independent of the reflectivity of any of the facets in which the light guiding region terminates. 
     
     
         18 . A method as claimed in  claim 16  in which the amplitude of the reflectivity of each reflecting means lies in the range 2% to 20%, and preferably, the amplitude of the reflectivity of each reflecting means lies in the range 5% to 15%, and advantageously, the amplitude of the reflectivity of each reflecting means is approximately 10%, and preferably, each reflecting means extends into the light guiding region, and advantageously, the light guiding region comprises an active region, and each reflecting means extends into the light guiding region to a location spaced apart from the active region, and advantageously, the outer two of the reflecting means define a volume in the light guiding region in which lasing occurs, and preferably, each reflecting means is formed by a slot located in the waveguide for providing the partial reflection of the light in the light guiding region adjacent the slot, and advantageously, each reflecting slot extends substantially laterally of the light guiding region, and preferably, at least some of the reflecting slots are at least partially filled with a reflecting medium, and advantageously, the waveguide is provided by a ridge waveguide having an elongated ridge extending longitudinally along the waveguide, the ridge defining the light guiding region, and each reflection causing means is located in the ridge. 
     
     
         19 . A method as claimed in  claim 16  in which the waveguide is of a semiconductor laser, and preferably, the waveguide is adapted for receiving a pumping current. 
     
     
         20 . A laser device as claimed in  claim 7  in which the first and second light guiding regions are passive regions, and alternatively, the first and second light guiding regions are active regions, and preferably, the laser device is of a buried waveguide structure.