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Examples of previous work

Our team has combined experience of more than 50 years in delivering technology to our parent company Sharp Corporation. Thanks to this, we have built comprehensive modelling capability and expertise in optics, device physics and thermal analysis which we are now able to offer to our customers.

Shaping of laser beams using a microlens array

Many applications using laser beams require modification of the laser beam profile and/or uniformity from how it is generally emitted from a laser source. For example in industrial applications, laser printing and lighting applications, a uniform irradiance (flat-top) will be most frequently used due to the fact that the same interaction of the beam is sought over the illuminated area.

The aim of this project was to focus a laser diode beam to a spot area less than 0.7 mm2 with a flat top intensity profile. We designed and optimised a specific microlens array (MLA) as a beam shaping homogeniser using both ray tracing and physical optics propagation (POP) in Zemax. The laser source was created in our simulation and experimental laser beam profile data such as near field pattern, divergence angle and astigmatism was used. MLA was fabricated according to our design.

The optical system using a focusing lens and the designed MLA was set up and laser beam shaped measured in our laboratory. The images show the optical set up in Zemax, the results of the Zemax simulation ray tracing and physical optics propagation and the measured beam profile. Target beam uniformity and beam size was achieved. The measured fringes pattern which is caused by the laser beam coherence interaction with the MLA is also well reproduced in the simulation.

Modelling of high power edge-emitting laser diode

We have developed expert knowledge of III-V and III-N edge emitting laser diodes. Simulation of lasing is a challenging problem and getting accurate results which can be trusted to contribute to product development requires a lengthy optimisation loop between experimental and simulated results. Here we show modelling of the near field pattern of a multimode ridge waveguide edge emitting laser diode. The calculated light output characteristic versus current is also shown. The calculation of different number of lasing modes illustrate how total output power can be affected in the simulation. A compromise of accuracy and computation time can then be made.

Heat dissipation analysis

Simulation of thermal dissipation of a watt class laser diode mounted in a standard TO9 can and then in a metal chassis. Convection cooling was included in the simulation and flow is illustrated by red arrows.

Design of waveguides for laser beam mixing

Combining red, green and blue laser beams in a small package is desirable for future applications in wearable devices. Free space optics are generally used but then reduction in size is limited. This project considered the use of silica (SiO2) waveguides as a beam combiner where each laser beam is coupled to a separate waveguide and brought within a few microns at the combiner output. Beam propagation simulation was developed using a combination of in house and commercially available software. Each of the waveguide branches was optimised for low loss propagation and minimised stray light. Results of our simulation show near field patterns at the output of the combiner for the three wavelengths. The beams were separated by about 5um at the output of the combiner which was sufficient for the application.

Power devices

High power GaN HEMT Transistors are very promising devices for new high power applications in renewable energy converters, electrical cars battery converters, data servers and any applications requiring high power density and reduction in form factor. Due to the high voltage used in these applications, temperature performance of GaN HEMT must be understood and optimised. We developed a temperature dependent HEMT device physics modelling capability. Device experimental results were used for our model calibration and a feedback loop simulation-experiment was then followed to improve the device performance. We show here an example of the 2D temperature map of the GaN HEMT device simulation after 0.01ms operation. The 1D plot report the temperature rise at the gate edge and in the silicon substrate. Simulation and measurement show very good agreement.