i-CLADISS A longitudinal laser diode model

Download brochure (PDF)

   
      Brief Description        
     

CLADISS was developed by the University of Gent over many years and has been the source of many publications. It holds a high reputation among the international modelling community. i-CLADISS is a development from the Gent version, bringing all the power of this model in a very easy to use Windows environment. It is a longitudinal laser diode model, ignoring all lateral effects (lateral effects are planned for a later version) but happily modelling multi-segment lasers, from simple FP lasers to comlex multi-contact, multi-segment frequency tunable DFB lasers. It is multi-mode and will generate threshold and DC characteristics, spectra, AC and FM response, up to 3rd order harmonic distortion effects, noise characteristics, including linewidth calculation, and large signal time domain response.

      
      Structure Specification        
     

A laser is defined by up to 20 discrete sections with each section having its own electrical contact. Here is a list of some of the parameters that can be set for each section:

  • dimensions - length, width and active layer thickness
  • grating parameters - gratings may be index or gain/loss gratings of any order and may also be chirped
  • optical parameters - reflection and transmission coefficients at each end of the section, facet scattering losses may also be included; material loss, vertical confinement factor.
  • thermal parameters - substrate temperature and thermal conductivities
  • electrical parameters - resistivity and injection efficiency
  • material - a named material is assigned to each section; see below
    		•       
        Material Speciation      
         

    A CLADISS material contains all the information to describe the gain function, refractive index etc:

  • Gain function - an 8 term equation defining the wavelength, carrier density and temperature dependence of carrier induced gain. Non-linear gain (power dependent) is also available.

    • (linear or logarithmic, polynomial also planned)

  • Gain supression function - a 10 term equation defining spectral hole burning effects with carrier density, wavelength and temperature dependence g(E,N,T)
  • Refractive index function - a 12 term equation, providing wavelength, carrier and temperature dependence
  • Intervalence band absorbtion - a 12 term equation. providing wavelength, carrier and temperature dependence: 
    		•       
          Device Editor        
         

    i-CLADISS includes an extensive device editor in its Windows version, fully mouse driven. This may be used to rapidly move, add new sections and edit existing ones, with utilities to graphically examine the various functions for gain, refractive index etc.

    		      
          Calculations        
         

  • Waveguide mode profiles for the given slab structures.

  • All radiation mode profiles for the given slab structures. These will correctly model any interference from multiple reflections.

  • Radiation mode directions and coupling coefficients.

  • Automatic calculation of resonance wavelengths of the various grating orders for a given grating period or, alternatively, resonance period for a given wavelength.

  • Direct DBR coupling coefficients for guided TE to TE and guided TM to TM modes, for the any grating order.

  • Indirect DBR coefficient through the radiation modes.

  • Radiation loss coefficients for all grating orders.

    •      All coefficients may be plotted as a function of:

  • wavelength

  • de-tuning from resonance

  • grating depth

  • any combination of waveguide dimension

    • The grating may be asymmetric and coupling coefficients are calculated for both forward and backward guided waves. For a single or multi-section device, the following may be calculated.

  • Longitudinal profiles of forward and reverse travelling guided modes in a length of grating.

    1. reflection and transmission coefficients versus wavelength

    2. reflection and transmission coefficients versus slab widths of the vertical layer structure.

    3. a Device General Scan will allow the user to generate plots as a function of any parameter in the device description file. This is achieved by supplying two device description files and creating a third device that is a weighted average of the two.

  • reflection and transmission coefficients versus wavelength

  • reflection and transmission coefficients versus slab widths of the vertical layer structure.

  • a Device General Scan will allow the user to generate plots as a function of any parameter in the device description file. This is achieved by supplying two device description files and creating a third device that is a weighted average of the two. In this way, you can determine the variation of the device response to any parameter of the device.

  • Radiation near and far field patterns from a finite length grating, for both upward and downward beams.

    • The waveguide may include absorption regions and the coefficients will correctly model these.

    		      
          Validity Testes        
         

    Mode profiles are accessible for inspection to ensure sensible operation. The results of validity tests against a variety of published figures will be supplied upon request.

    		      
          Other Notes        
         

    This version has no facilities for taking account of lateral effects, for example the horizontal guiding in structures such as mesas and ridges. The model will run on an IBM PC compatible. Facilities are provided for printing out all graphs in publication quality to Epson LQ's, Laserjets, Paintjets, HPGL plotters, Deskjets, Postscript printers and others. Many drivers have colour capability. All results are also be available in ASCII file format.