Device with quantum well layer

Abstract

A device for guiding and absorbing electromagnetic radiation, the device including: absorbing means for absorbing the electromagnetic radiation; and a coupled to the absorbing means for guiding the electromagnetic radiation to the absorbing means, wherein the waveguide and the absorbing means are formed from a structure including a first cladding layer, a second cladding layer over the first cladding layer, and a quantum-well layer between the first and second cladding layers, the quantum-well layer being formed of a material having a different composition to the first and second cladding layers, wherein the thickness and the composition of the quantum-well layer is optimised to provide an acceptable level of absorption of electromagnetic radiation in the waveguide while providing an appropriate band gap for absorption of the electromagnetic radiation in the absorbing means.

1 - 15 . (canceled) 
     
     
         16 . A device for guiding and absorbing electromagnetic radiation, the device comprising:
 absorbing means for absorbing electromagnetic radiation of a select wavelength;   a waveguide coupled to the absorbing means for guiding the electromagnetic radiation to the absorbing means, wherein the waveguide and the absorbing means are formed from a structure having a first cladding layer, a second cladding layer over the first cladding layer, and a quantum-well layer between the first and second cladding layers, the quantum-well layer being formed of a material having a different composition relative to the first and second cladding layers, wherein a thickness and the composition of the quantum-well layer being configured to provide a select level of absorption of electromagnetic radiation in the waveguide while providing a select band gap for absorption of the electromagnetic radiation in the absorbing means.   
     
     
         17 . A device according to  claim 16 , comprising:
 a substrate, wherein the waveguide and the absorbing means are provided on the substrate and the absorbing means includes at least one resonator, each of the at least one resonators being resonant at a predetermined wavelength of the electromagnetic radiation.   
     
     
         18 . A device according to  claim 17 , wherein the select level of absorption in the waveguide is a minimum level of absorption obtainable within a predetermined range of thicknesses and compositions of the quantum-well layer, such that the thickness and composition of the quantum-well is selected to minimise absorption in the waveguide. 
     
     
         19 . A device according to  claim 17 , wherein the thickness and the composition of the quantum well are configured to provide a desired quantum well band gap while maximising a quality Q factor of resonance of the resonators and keeping strain within an active layer lower than a maximum specified value. 
     
     
         20 . A device according to  claim 19 , wherein the maximum specified value is 1.5%. 
     
     
         21 . The device according to  claim 16 , wherein the quantum-well layer has a thickness that is substantially less than a thickness of the waveguide. 
     
     
         22 . A device according to  claim 16 , wherein the device is a spectrometer. 
     
     
         23 . The device according to  claim 22 , wherein the quantum-well layer is configured to have a composition and thickness providing a band-gap that is less than or equal to a predetermined energy, the predetermined energy corresponding to a maximum wavelength Amax of electromagnetic radiation that the spectrometer is configured to detect. 
     
     
         24 . The device according to  claim 23 , wherein the resonators have a minimum free-spectral range FSR value corresponding to a wavelength interval Δλ, and the quantum well layer is configured to have a composition and thickness providing a ground state transition energy corresponding to an energy of radiation at a wavelength λmax+Δλ. 
     
     
         25 . A method of optimising a layer thickness and composition of a quantum-well layer of a device for guiding and absorbing electromagnetic radiation, the device including:
 a substrate;   absorption means located on the substrate for absorbing the electromagnetic radiation; and   a waveguide on the substrate, the waveguide being coupled to the absorption means for guiding the electromagnetic radiation to the absorption means, wherein the waveguide and the absorbing means are formed from a structure having a first cladding layer, a second cladding layer over the first cladding layer, and the quantum-well layer between the first and second cladding layers, the quantum-well layer being formed of a material having a different composition relative to the first and second cladding layers, the method comprising:   determining a desired quantum well ground state transition energy for the quantum-well layer for absorption of the electromagnetic radiation in the absorbing means; and   determining a thickness and composition of the quantum well that are configured to provide the desired quantum well ground state transition energy and to provide a select level of absorption in the waveguide.   
     
     
         26 . A method according to  claim 25 , wherein the devices includes at least one resonator, each of the at least one resonators being resonant at a predetermined wavelength of radiation and wherein determining the thickness and the composition comprises:
 determining the thickness and the composition that are configured to provide the desired ground state transition energy, while maximising a quality Q factor of resonance of the resonators and keeping strain within the quantum-well layer lower than a predetermined limit.   
     
     
         27 . A method according to  claim 26 , wherein determining the thickness and the composition of the quantum well comprises:
 selecting an initial thickness and composition of the quantum-well layer from a predetermined range of thicknesses and compositions;   determining a bend loss in the at least one resonator based on the initial thickness and composition;   obtaining a value of the Q factor for the resonator, based on the bend loss;   determining whether the obtained value of the Q factor is a maximum available value of the Q factor within the predetermined range of thicknesses and compositions;   obtaining a value of strain in the quantum-well layer based on the selected thickness and composition;   
       determining whether the obtained value of the strain is below the predetermined acceptable limit; and
 using the selected thickness and composition as a final thickness and composition of the quantum-well layer, if it is determined that the value of the Q factor is a maximum available value, and if the obtained strain is below the predetermined acceptable limit. 
 
     
     
         28 . A method according to  claim 27 , comprising:
 if it is determined that the value of the Q factor for the initial thickness and composition is not a maximum value or if the obtained strain is not below the predetermined acceptable limit, adjusting the initial thickness and composition to obtain a new thickness and composition and repeating the steps of obtaining a bend loss, determining a Q factor value, determining whether the obtained value is a maximum, obtaining a strain value and determining whether the obtained strain value is below a predetermined acceptable limit for the new thickness and composition.   
     
     
         29 . The method of  claim 28 , wherein the initial thickness and composition are selected based on a target value of a band gap for the quantum-well layer. 
     
     
         30 . The method of  claim 29 , wherein the at least one resonator has a minimum free-spectral range FSR value, the method comprising:
 obtaining a wavelength difference value that is less than a minimum FSR value of a plurality of resonators; and   obtaining the target value of the band gap by obtaining a value corresponding to the energy of radiation at a wavelength equal to a sum of the wavelength difference value and the predetermined wavelength.   
     
     
         31 . A device according to  claim 20 , wherein the device is a spectrometer. 
     
     
         32 . The device according to  claim 31 , wherein the quantum-well layer is configured to have a composition and thickness providing a band-gap that is less than or equal to a predetermined energy, the predetermined energy corresponding to a maximum wavelength Amax of electromagnetic radiation that the spectrometer is configured to detect. 
     
     
         33 . The device according to  claim 32 , wherein the resonators have a minimum free-spectral range FSR value corresponding to a wavelength interval Δλ, and the quantum well layer is configured to have a composition and thickness providing a ground state transition energy corresponding to an energy of radiation at a wavelength Δmax+Δλ.