Wavelength control of multi-wavelength laser

While lasers are now essential in numerous industrial fields from telecommunication to sensing, many applications require the simultaneous or sequential use of different wavelengths. This imposed the use of either many different lasers or so-called “tunable” lasers. The former requires optical switches, robust micrometer precision of several optical elements, simultaneous control and monitoring of several lasers, thus leading to bulky and complex systems. On the other hand, tunable lasers only emit a single wavelength at once, tuning is slow (several microseconds or longer) and can require complex commands.

Solution

Multi-wavelength lasers – devices having the capability to selectively emit at different wavelengths – have been proposed but the lack of an efficient and precise control mechanism made them unsuitable.
The VUB Brussels Photonics Team B-PHOT, in collaboration with the Institute for Applied Physics of the Technical University Darmstadt, has developed a wavelength control system for multi-wavelength lasers to combine the best of both worlds. The all-optical control loop is monolithically integrated with the laser and gives precise control over the multi-wavelength emission through a single control voltage parameter. It allows to precisely balance the different emission wavelength – e.g. to reliably obtain equal output power at different wavelengths – or quickly switch between wavelengths at the nanosecond timescale. The control system is compatible with generic platforms and mass manufacturable.

Competitive advantages

Single control parameter
High wavelength suppression ratio (> 30-50 dB)
Fast switching capability (nanosecond range)
Monolithic integration with the laser
Small footprint: < 0.7 mm² on Indium Phosphide
Low power consumption (< 1 mW)
Compatible with generic foundry platforms

	Multiple separated lasers	Tunable lasers	Multi-wavelength lasers with control system
Simultaneous emission	Yes	No	Yes
Wavelength tuning	Fast (require ext. switches)	Slow	Fast
Single chip (monolithic integration)	No	Yes	Yes
Control mechanism	Simple / Several control parameters	Complex	Simple / one parameter
Footprint	Large	Small	Small
Power consumption	High	Low	Low
Applications	Optical Communication (DWDM)	Optical Communication (DWDM typ. spare device), Fiber-sensor interrogation

Current drawbacks

Control system designed for a specific laser/set of wavelengths
Finely tailored design required for wide wavelength separation
Risk of dynamical instabilities when aiming for ultrafast control or very high suppression ratio

Ongoing developments

Improvements of the control efficiency for a wide range of laser configurations (including current and temperature settings)
Optimization of the system against wavelength separation mismatch to reduce customization needs.
Improvement of the dynamical stability

Optical spectra of a multi-wavelength laser sequentially switching between three wavelengths due to an increasing voltage applied in the control section.

Looking for

Setting up joint R&D collaborations with industrial partners for upscaling of the control system and for targeting specific industrial use cases.
Entering into license agreements or partnerships to implement the design into industrial products

Contact

Hugo Loosvelt

IP & Licensing Manager

hugo.loosvelt@vub.be

Brussels Photonics (B-PHOT)
Martin Virte
[E] martin.virte@vub.be

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