Advanced heater module for long range thermal tuning: Sketch of three application cases utilizing the advanced heater module. From left to right: Long phase shifts in optical delay lines; more than 4Pi shifts in MZIs; and large tuning range of ring resonators for filters or for shifting the resonances of a generated optical frequency comb.

“The new advanced heater module gives access to very high local temperatures and in such a way can heat the silicon nitride waveguide and change its temperature-dependent refractive index. For example, it is used to tune wavelength selective filters by large tuning ranges, MZIs by several pi phase shifts, long delay lines by long phase shifts or ring resonators for frequency comb generation by more than one full free spectral range obtaining more than 4nm of tuning. This is used for telecom and datacom applications as well as spectroscopy and metrology where large tuning ranges are needed,” stated Dr. Michael Geiselmann, Managing Director.

The newly available heater module is optimized for LIGENTEC’s all-nitride AN800 process with waveguides that offer low bending radii (< 0.005 dB for 10 turns of 50um radius), low coupling losses (< 1 dB/facet), low propagation losses (< 0.1 dB/cm) and high power handling (up to 10 W tested). The company said that the heater material can support very high temperatures.

Compared to aluminum based heater materials, LIGENTEC’s product is much more stable at high temperatures: above 500° C. Furthermore, it is fully compatible with large scale CMOS fabrication lines, which makes scaling to volume easy.

Designed using Lumerical’s DEVICE Suite, the LIGENTEC heater module is responsive and stable over an ultra-broad tuning range. According to the company, a ring resonator with a free spectral range (FSR) of 500 GHz (resonance separation of 4 nm) can be tuned by more than 4 nm operating at telecom wavelength range, thus covering a full tuning of the FSR. Similarly for MZIs, multiple pi-phase shifts are possible.

The company indicated that Lumerical’s simulation tool, DEVICE HEAT, was essential to the design phase of product development since it takes into account the material properties and heat coefficients of silicon nitride and glass, linking these factors directly to the optical mode problem solver within the design software.

Lumerical’s DEVICE Suite performs multiphysics simulation of heat and electrical conduction, combined with photonics simulation, including relevant material models in each physical domain. It is an ideal platform for designing photonic integrated circuits (PICs) targeted for LIGENTEC’s All-Nitride (AN) process. Due to the significantly low loss characteristic of LIGENTEC’s AN core technology, the fidelity of imported material data is critical to simulation quality. With its HEAT and CHARGE solvers, Lumerical’s DEVICE Suite provides multiphysics simulation capabilities and workflows to model the interaction between optical, electrical and thermal effects at the physical level.

Source: https://data.angel.digital/pdf/PIC%20Magazine%20Issue%202%202020%20r2.pdf