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RATRO (LED)

Products > RATRO (LED)

RATRO — RAy-TRacing SimulatOr of Light Propagation

See also SimuLAMP software for optical and thermal design and optimization of LED lamps and arrays

1. Software overview


Fig. 1. 2D distribution of light emission from active region
The device-engineer oriented software tool RATRO (RAy-TRacing SimulatOr of Light Propagation) is designed for modeling the light extraction from LED chips. It involves ray-tracing simulation of the light propagation from the active region, absorption and extraction from the LED die through the n- and p-contact layers and the wafer, providing the integral extraction efficiency and the radiation patterns of the emitted light.

Distribution of the light emission from the active region is calculated in SpeCLED and stored in the file imported into RATRO™ along with the heterostructure geometry. Patterned and ordinary surfaces of contact layers, electrodes, and wafer are supported.

Progress in simulation is visualized in a solution-monitor window providing information on the percentage of traced rays. The computation is stopped automatically when all rays are traced.

The computed distributions of light propagation allow determination of the light extraction coefficients, fractions of light extraction through all chip surfaces, and energy loss in each chip region.


Fig. 2. Light extraction from a LED die with heat sink at the wafer bottom
RATRO 2008 shares the same graphical user interface (GUI) with SpeCLED 2008 to specify the chip geometry, while all input parameters specific for light extraction simulation are specified in RATRO tab. The results of the computation can be stored in ASCII files (*.cgs) and then viewed by the visualization tool SimuLEDView supplied within the RATRO tool. The visualization tool provides information on the integral light extraction parameters, 3D distributions of light intensity in the near-field, 2D distributions of light intensity visualizing the near-field and far-field regions, and radiation patterns. The SimuLEDView tool allows export of the 2D distributions in a bmp-image format and of 1D distributions extracted for selected directions in a text-table format.

2. RATRO 2008


Fig. 3. Radiation pattern in the top hemisphere
The RATRO package provides ray-tracing simulation of the light propagation from the active region, absorption and extraction from the LED die through the n- and p-contact layers and the wafer, providing the integral extraction efficiency and the radiation patterns of the emitted light. The code implements the physical models of optical processes, based on the following assumptions:

  • The emission from the active region is symmetrical so that the total light intensity and radiation pattern are identical for both sides (top and bottom) of the active region.
  • Angular emission distribution from the active region can be specified as (I) uniform, (II) Lambertian, or (III) custom (user-defined table).
  • The active region emits monochromatic radiation. The effect of the radiation wavelength is accounted implicitly via the refraction coefficients assigned for each material.
  • The light transmission and reflection in the metal electrodes can be calculated from known material parameters or specified as user-defined transmission and reflection coefficients.

The input of necessary data generated by SpeCLED, specification of optical parameters, running and monitoring of simulation, and visualization of the results is done via Graphical User Interface (GUI) and SimuLEDView visualization tool, respectively. RATRO is supplied with the user manual and description of physical model.


Fig. 4. Light extraction from an LED die with a shaped wafer

3. Support

Hot-line support can be provided for customers. The support includes free of charge supply of updated versions released during the license period and technical consulting on RATRO operation.

4. Key Publications

 

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