A monolithic, chip-based spectrometer based on the novel concept of a series of electrically addressable high-Q
resonators coupled to a ridge waveguide is presented. A discrete monolithic InP-based spectrometer chip has been
designed to detect wavelengths spanning a 10nm range in the near-infrared region functioning as a sensor. This
spectrometer approach has a number of advantages over traditional spectrometers. As well as being solid state and
having no moving parts, the co-location of wavelength dispersion and detection offers advantageous spectral
performance in a compact chip form. Optimization of resonator size and composition to detect wavelengths across the
spectral range of interest will be discussed together with preliminary experimental results.
Great efforts and vast investments have been put into the research and development of widely tunable lasers in the last
25 years. Tunable lasers have become critical components in the implementation of next generation telecommunication
networks and systems, to provide dynamic wavelength provision for channel restoration, reconfiguration and protection.
Some stringent requirements have been imposed on tunable lasers by telecommunication applications. Consequently,
ultra-high optical output power (⩾100 mW), wide tunability (tuning range ~ 40nm), narrow linewidth (< 2MHz), and
side-mode suppression ratio (SMSR > 40dB) have become the main objectives for the development of the future
telecommunication tunable lasers. Facet output power is the fundamental decisive factor among these targets. Original
design ideas and novel approaches to the design of ultra-high power InGaAsP/InP based multisection widely-tunable
laser gain section have been reported by the authors previously, mainly including: firstly, a bulk balance layer structure
is placed above the InP buffer layer and below the MQWs stack, which enables a large reduction of free-carrier
absorption loss by greatly shifting the optical field distribution to the intrinsic and n-doped sides. Secondly, an InP
spacer layer is placed below the ridge and above the multiple quantum wells (MQWs) stack, so as to introduce extra
freedom in the control of widening the single mode ridge width. This paper will focus on the optimization on the
implementation of the above design ideas and approaches, regarding single mode ridge width, optical confinement in
the MQWs, optical overlap with the p-doped epilayers, output power, threshold current, and slope efficiency.
Novel materials, micro-, nano-scale photonic devices, and 'photonic systems on a chip' have become important focuses for global photonics research and development. This interest is driven by the rapidly growing demand for broader bandwidth in optical communication networks, and higher connection density in the interconnection area, as well as a wider range of application areas in, for example, health care, environment monitoring and security. Taken together, chalcogenide, heavy metal fluoride and fluorotellurite glasses offer transmission from ultraviolet to mid-infrared, high optical non-linearity and the ability to include active dopants, offering the potential for developing optical components with a wide range of functionality. Moreover, using single-mode large cross-section glass-based waveguides as an optical integration platform is an elegant solution for the monolithic integration of optical components, in which the glass-based structures act both as waveguides and as an optical bench for integration. We have previously developed a array of techniques for making photonic integrated circuits and devices based on novel glasses. One is fibre-on-glass (FOG), in which the fibres can be doped with different active dopants and pressed onto a glass substrate with a different composition using low-temperature thermal bonding under mechanical compression. Another is hot-embossing, in which a silicon mould is placed on top of a glass sample, and hot-embossing is carried out by applying heat and pressure. In this paper the development of a fabrication technique that combines the FOG and hot-embossing procedures to good advantage is described. Simulation and experimental results are presented.
Widely tunable ultra-high power monolithic multi-section tunable lasers have been a sought after dream for more than two decades. In recent years, tunable lasers have become critical components in the development of the next generation telecommunication networks and systems, due to their unique attributes and flexible functionalities. However, some stringent requirements have been imposed on tunable lasers by telecommunication applications regarding their tuning range, optical output power, side-mode suppression ratio (SMSR), linewidth, chirp, tuning speed, reliability, and so on. In addition, monolithic tunable lasers, requiring a regrowth process, suffer from butt-joint reflections from the regrowth interfaces of these multi-section devices, which have seriously affected their tunability, and greatly reduced their facet output power. Butt-joint reflection losses between active-passive interfaces are therefore the crucial and decisive factors in multi-section tunable laser operation. In this paper, original design ideas and novel approaches to the design of ultra-high power InGaAsP-InP based multi-section widely-tunable lasers are introduced. Simulation results show that the facet output power in the proposed new design can be greatly increased compared with a conventional design. The optimized butt-joint angles and the arrangements of these angles at the active-passive interfaces in a multi-section tunable laser can largely reduce the total adverse interface reflection in the device, and tremendously improve the operation performance of the multi-section tunable laser. Finally, an integrated curved semiconductor optical amplifier design is introduced that would be able to futher increase the total optical output power of the device and reduce the backward optical reflection into the device.
We previously demonstrated light guiding in fiber-on-glass (FOG) dielectric waveguides using fluoro-tellurite glasses.
These waveguides were fabricated by mechanically pressing a fiber onto a polished planar glass substrate of lower
refractive index above the glass transition temperatures. However, two handling constraints have been discovered in this
approach. In practice, for novel inorganic compound glasses, the minimum dimension of fiber that can be handled is
preferably around 30μm. The minimum refractive index difference between the fiber and the substrate that can be
reliably achieved at present with these glasses is 0.01. Our simulation results showed that, taken together, these
restrictions provide a practical barrier to achieving single-mode FOG operation at telecommunications wavelengths.
Here we present simulation and experimental results for a new inorganic glass FOG waveguide that simultaneously
meets these handling constraints and achieves mono-mode operation around 1.55 μm. In this new design, a
homogeneous glass fiber is partially embedded lengthwise in a substrate of higher refractive index glass; the nonembedded
part of the fiber is air clad. Simulation results presented for fluoro-tellurite FOG waveguides confirm the
success of the new design in realizing single-mode propagation at 1.55 μm for a fiber diameter of 30 μm and a fibersubstrate
refractive index difference of 0.01. The design is robust, with good dimensional fabrication tolerance, but
predicted losses are over 6 dBcm<sup>-1</sup>. A proof-of-principle demonstrator is fabricated using two commercially available
multi-component silicate glasses (Schott F2 and F4). This shows multimode waveguiding at 0.633 μm, guidance around
a curve, and appears mono-mode at 1.575 μm.
High power widely tunable lasers are extremely desirable for telecom applications as a replacement for distributed feedback (DFB) lasers in wavelength division multiplexing (WDM) systems, due to their dynamic provision properties. They are also sought after for many other applications, such as phased radar systems, optical switching and routing. This paper introduces novel design ideas and approaches on how to achieve ultra high power in the design of an InGaAsP-InP based widely tunable laser gain section. The inventive ideas are basically composed of two parts. Firstly, to increase the facet optical output power by the inclusion of an InP spacer layer below the ridge and above the multiple quantum wells (MQWs) stack, in order to have extra freedom in the control of widening the single mode ridge width. Secondly, to reduce the free-carrier absorption loss by the inclusion of a bulk balance layer structure below the MQWs stack and above the buffer layer, so as to largely shift the optical mode distribution to the intrinsic and <i>n</i>-doped side of the epilayer structure where the free-carrier absorption loss is lower than that of the <i>p</i>-doped side. Simulation results show that the proposed epilayer designs of the ultra high power gain sections would greatly increase the facet optical output power of a tunable laser, by up to about 80%. It should be noted that these novel epilayer design ideas and approaches developed for the gain section are applicable to the designs of ultra high power DFB lasers and other InGaAsP-InP based lasers.