The Company has developed a fully integrated platform of optical and photonic capabilities combining a range of 3D waveguides, precise alignment features for fiber interconnects and micro-optic components. The Company’s technology uses laser based manufacturing to directly write optical waveguide circuits and micromachined structures within a block of glass. Integrating these micro-structures provides new levels of fiber coupling and significant relaxation of optical transceiver design constraints in terms of layout, assembly and packaging. Additionally, laser-based scribing simplifies manufacturing to a two-step process that delivers low signal loss, high density and scalable products. These compact glass-based 3D photonic integrated circuits are produced using the Company’s in-house fast wafer scale processing capabilities.
Wafer-scale laser-inscribed optical structures
Optoscribe has developed an ultra-short pulse laser system to directly modify and manipulate the structure of glass. A single laser beam produces ultrashort pulses with high peak powers, tightly focused inside the bulk of the glass. At this focal point, non-linear light absorption generates a permanent, local structural change. This structural change can manifest in many different ways, but the two key modalities Optoscribe deploys to engineer optical structures are a refractive index change and an etch rate enhancement.
The refractive index change is used to create waveguides in three dimensions inside the bulk of the glass, while the etch rate enhancement (of between 500 and 1000 times that of non-irradiated glass) is used to create physical 3D microstructures in the glass. To complete the creation of the physical microstructures, the glass is then subject to a wet chemical etch that preferentially etches away those areas that have been irradiated by the laser, while the remainder of the glass remains unaffected.
3D photonic integrated circuits
Using a standard off-the-shelf laser and borosilicate glass well suited to photonic integration, the innovative aspects of this method lie in the low latency optical system and bespoke software that controls and automates the entire component manufacture process from design through layout to fabrication.
In Optoscribe’s state-of-the-art manufacturing facility, waveguide fabrication is both rapid and accurate, with the system tightly controlling cross section, size and shape to provide very well-defined waveguide polarization behaviour and a wide library of standard subcomponents, including Y splitters, directional couplers, multimode interference (MMI) couplers and slab couplers. Meanwhile, high precision optical structures such as ‘V’ grooves for passive fiber alignment, total internal reflection (TIR) mirrors for light turning and other micro-optic assets can be fabricated via the etch rate enhancement technique.
As these two different types of structures are created during the same laser process, excellent co-alignment between waveguides and microstructures can be achieved, allowing complex 3D photonic integrated circuits to be realized in a fast, simple and affordable process. Such compact monolithic glass chips are ideal for integration into next-generation transceivers.
In long range telecommunications, this demand is currently met by Wavelength-division multiplexing (WDM) and coherent detection techniques, to increase network bandwidth on a singlemode fiber (SMF). To date, this has enabled optical transport networks to increase network bandwidth and meet demand. However, the capability of such approaches to continue increasing the available bandwidth will soon diminish. In an impending capacity ‘crunch’ caused by the Shannon nonlinear limit an alternative approach to data multiplexing will be required. Moreover, the cost of increasing spectral efficiency up to the Shannon limit will become prohibitively expensive. Click to read more