LNOI DEMONSTRATORS

Quantum sensing requires specific and complex arbitrary optical waveform generators in the 780-800 nm range to address atoms and ions.

THALES is currently developing two quantum sensors, one using cold atom sensors operating at 780 nm, and the other based on rare-earth ions doped into solids operating at 793 nm. Their practical usage, however, is limited at present because they are barely portable.

To go beyond the state of the art, a fully integrated optical source for quantum sensors with frequency conversion, IQ modulators, filters, frequency shifters and fast switches will be implemented on the LNOI PIC platform.

Schema of prototype #1: Quantum sensing demo

A passive resonant optical gyroscope (RFOG) is an alternative to the standard ring laser gyroscopes or the interferometric fibre optical gyroscope. THALES is currently developing several approaches based on standard or hollow-core fibres and has patented a solution to address the backscattering issue that affects resonant optical gyroscopes preventing precise low rotation rate measurements).

ELENA’s LNOI PIC meets both the required performances and the operational constraints and can replace the current set of fibre-coupled components that are not compact enough, not energy-efficient and sensitive to thermal drifts and vibrations. The PIC architecture may include several phase modulators, I/Q modulators or more innovative approaches for frequency shifting. Thanks to the fast lead time of the CSEM technology, Thales will be able to implement several architectures and test PICs on its existing resonant gyroscopes.

Schema of prototype #2: Resonant optical gyroscope

At present, LNOI modulators are the best choice for telecom payload systems thanks to their linearity and high optical power handling. However, they only partially meet the constraints of size, cost and power consumption. ELENA will overcome these limitations thanks to the high chip density and energy efficiency. ELENA will also set new standards for analogue applications in terms of linearity, pure phase modulation and low spurious behaviour.

The ELENA partners THALES and ROSENBERGER will apply this advanced LNOI technology in their specific RF optical transceiver designs.

This prototype shall demonstrate the high dynamic range, high bandwidth and high efficiency (in a very compact design) as well as high RF power handling. It also allows to test new ideas within the scope of the new LNOI technology platform.

Schema of prototype #3: RF optical transceivers for telecom and space applications.
Left: Rosenberger prototype using arrayed MZ modulators on same wavelength using power splitter.
Right: Thales prototype using arrayed MZ modulators in WDM configurations using passive mux/demux.

Data packet routing and switching in metropolitan telecom networks can be achieved by wavelength switching. This requires a wavelength-tunable laser that can switch its output frequency in nanoseconds. To address this challenge, a sampled grating distributed Bragg reflector laser [1] has been reported within a monolithic InP platform with a switching time around 6 ns. In an alternative approach, III-V Lab has shown a III-V on SOI laser suitable for optical packet-switched networks [2].

Schema of prototype #4, a fast tunable laser, comprising an InP semiconductor, optical amplifiers, (SOA)chip and a LNOI fast-switching circuit (electrodes not represented).

In this hybrid configuration, the optical gain of the laser is provided by the III-V medium, and the passive parts of the cavity are made inside the silicon chip. An adiabatic taper couples the light from the silicon waveguide to the III-V medium. A fast p-i-n junction-based tunable filter made of two rings resonators (RRs) in a Vernier configuration enables wavelength tunability of the laser. The Si filter is electrically tuned by using the plasma dispersion effect in the p-i-n junction in a carrier injection mode. Because parasitic thermal effect has a response time in the micro-second timescale [3], there is a real need to switch to a faster tuning mechanism for the mode selecting filter.

In an LNOI PIC platform, ELENA expects to eliminate the parasitic Joule effect in the p-i-n junction on Si platform. ELENA’s ambition is to show a fast wavelength switching within the enlarged C+L band (> 90 nm spectral range). ELENA also aims to demonstrate a fully integrated fast tunable laser with a LNOI fast MZ modulator: a C+L band fast tunable 25-Gbaud QPSK transmitter will be demonstrated by leveraging the ELENA technologies.

WHAT this prototype shall demonstrate:

• < 2 ns wavelength switching for all channels in a > 40 nm bandwidth

50 GBau I/Q modulation

Schema of a fast tunable transmitter, comprising a fast tunable laser and an LNOI I/Q modulator, which is integrated on the same LNOI chip as the filter and Sagnac mirror of the laser. DC and RF routing lines are not represented.