I have spent a bit of time over the past few days looking into the development of silicon-polymer hybrid modulators. My interest of course being that I want to investigate if there is a path forward for POET to implement this for future applications.

A very good article documenting the subject was published last summer by Nature Communications (open access): High-temperature-resistant silicon-polymer hybrid modulator operating at up to 200 Gbit s−1 for energy-efficient datacentres and harsh-environment applications. Prepared by Nissan Chemical Corporation and The Institute for Materials Chemistry and Engineering (Japan). Side note  the Nissan Chemical Corporation was founded in founded in 1887 as Japan’s first manufacturer of chemical fertilizers…it is a very large and very interesting company.

https://www.nature.com/articles/s41467-020-18005-7#change-history

First we need to  recognize that the EO modulator is applied to the output of a continuous wave laser. Suresh provided a simplified description of the operation to that of a shutter. The EO modulator currently comes into play for POET at 400G designs. 100G and 200G POET applications use directly modulated DFB (Distributed-Feedback) lasers where the optical beam is modulated by on/off current injection to the laser diode.

As we know POET has created an industry first with flip chip DML lasers producing a very compact, low cost optical engine with eye opening data transfer clarity.

The flip-chip assembly technique enables a true single-chip, fully integrated optical engine to be produced at wafer-scale, resulting in the lowest-cost, smallest-size 100G CWDM4 optical engine with a form factor of nine millimetres by six millimetres, while including banks of four lasers, four monitor photodiodes, four high-speed photodiodes, a multiplexer, demultiplexer, taps for power monitoring and features supporting a self-aligned fibre attach unit.

Now let me share some of the interesting takeaways and quotes from the silicon-polymer hybrid modulator article above.

To reduce the ever-increasing energy consumption in datacenters, one of the effective approaches is to increase the ambient temperature, thus lowering the energy consumed in the cooling systems. However, this entails more stringent requirements for the reliability and durability of the optoelectronic components.

The rapid growth in datacentre’s count and power density is leading to a dramatic increase in demand for energy. It is predicted that by 2025, datacentres will account for 20% of worldwide electricity consumption1,2. The cooling systems alone may account for up to 40% of the energy demands of a datacentre3. Therefore, to increase energy efficiency in datacentres, one effective solution is to raise the operating temperature, thus lowering the energy consumption in the cooling systems. Four per cent operating costs could be saved from cooling for every 1 °C increase in operating temperature4. However, this puts forward higher requirements for the reliability and long-term stability of the components in the datacentres, especially transceivers, at high ambient temperatures. As one of the key components in the transceiver, electro-optic (EO) modulators have been implemented on several photonic platforms, such as silicon5,6,7,8, indium phosphide (InP)9,10,11, organic12,13,14,15,16, lithium niobate17,18,19,20,21,22 and plasmonics23,24,25,26,27,28,29, each with their own advantages, such as enabling the integration with complementary metal-oxide-semiconductor (CMOS) electronics, low drive voltages, ultra-high bandwidths up to the terahertz regime22,23,24 and small footprints. Considering the ever-increasing energy consumption and emerging applications in harsh environments, apart from the aforementioned aspects, the reliability of the EO modulator at high ambient temperatures is another important aspect to be investigated. Recently, several directly modulated quantum-dot30 and distributed feedback (DFB)31,32 lasers have been successfully demonstrated operating at an elevated temperature of up to 80 °C with data modulations at 25 and 53 Gbaud, respectively.

My comment: Note that POET’s CWDM4 DFB laser power output graph was provided at up to  75’C (167’F) in the genius video.

On the other hand, external EO modulators incorporating organic EO materials, such as silicon-polymer hybrid (SPH), silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) modulators, have shown outstanding thermal reliability owing to the intrinsic high glass transition temperatures (Tg) of the deployed organic EO materials25,29,33,34,35,36. We have recently reported a thermally stable EO polymer modulator demonstrating stable performance of its static parameter (half-wave voltage, Vπ) at elevated ambient temperatures up to 105 °C for 2000 h33. Thereafter, we have further optimized the shape, the nonlinearity and the Tg of the EO polymer using advanced molecular engineering, and improved the electronic and photonic circuits, especially the electrode design.

The question of lifetime associated with the organic materials does not appear to be addressed by the article and remains unanswered.

What needs to be recognized is that device suppliers are not competition to POET but potential suppliers to  POET. I think of the POET Optical Interposer platform as a connectivity platform with outstanding filtering and thermal management capability. The connectivity allows for very low parasitics enabling exceptional high speed signal fidelity. This allows the designer the flexibility to choose from a diverse field of devices for integration.