DBR Calculator DBR Coupling Calculator version 2.5

   
     

A more formal Program Specification is also available.

  • DBR coupling coefficients for any order guided mode

  • radiation loss (locates all radiation modes) 

  • TE and TM polarisations 

  • sinusoidal, trapezoidal or user defined grating profiles 

  • arbitrary vertical layer structure, including MQW's and GRIN's

  • lossy waveguides 

  • any grating order 

  • multiple grating structures (stacked vertically) 

  • reflection and transmission coefficients for length of grating

  • resonance curves 

    This model is designed to calculate the coupling between guided modes in a planar distributed Bragg reflector struc-ture for the design of DFB lasers and other grating coupled waveguide ele-ments. The model will also calculate the effect of radiation loss from the grating.

    The model is very powerful and has been designed to be quite general, dealing with waveguides of almost arbitrary vertical section, including graded index sections and structures with two or more gratings stacked above each other. The model may, for example, be used to design structures with substrate reflectors designed to reduce radiation loss, or structures with two gratings placed so that their radiation beams cancel out.

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    Reflection and transmission coefficients of a 1mm long DBR structure as a function of detuning from the grating resonance. The resonance peak and sidebands are apparent. The asym- metry is due to interference effects between the radiation modes.

    		   
                 
          Some of the data provided by the model: 
  • Guided and all radiation mode pro-files. All radiation modes are auto matically located.
  • Resonance wavelengths and reso-nant grating period for a given grating order? DFB and radiation loss coefficients; plots as a function of grating depth, wavelength and waveguide dimensions are provided. The total radiation loss to all radiation modes is given.
  • Indirect DFB coupling coefficient modelling the effect of interference be-tween forward and backward waves.
  • Reflection and transmission coefficients of a length of grating; plots versus grating depth, wavelength, grating length or any waveguide dimension are provided.

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    The structure of a 3 quantum well GRIN-SCH-DFB laser 
    modelled using this Calculator. The model is happy dealing 
    with complex structures as these. Material loss may also be 
    introduced into the waveguide.

    		    
         

    The model is based on coupled mode theory. The theory also includes the effect of interference between the radiation beams in a manner similar to Kazarinov‡, but extending the theory to a more gen-eral case of any grating order and also asymmetric gratings.