Astronomical instrumentation is traditionally costly, large, and alignment-sensitive owing to the use of bulk optics. The use of integrated photonic devices in astronomical instrumentation can mitigate such drawbacks in certain applications where high light throughput and spectral bandwidth are less crucial. In this work, we present an ultra-compact carbon dioxide detection scheme using a single silicon waveguide ring resonator. The comb-like absorption line spectrum of CO2 around 1580 nm wavelength can closely match the comb spectrum of an appropriately designed ring resonator. By actively correlating such a ring spectrum with the CO2 absorption lines, a specific detection signal can be generated. We design the free spectral range of a ring resonator to match the absorption line spacing of carbon dioxide lines in the range from 1575 to 1585 nm. Using thermo-optic modulation, the ring resonator drop or through port transmission spectrum can be shifted back and forth across the incoming CO2 light spectrum, resulting in a modulated signal with an amplitude proportional to the CO2 absorption line strength. Furthermore, high frequency modulation and lock-in detection can result in a significant improvement in the signal to noise ratio. We demonstrate that such a device can provide real-time carbon dioxide detection for applications in ground- and satellite-based astronomy, as well as remote atmospheric sensing, in a compact package. In future work, such a sensor can be adapted to a range of gases and used to determine radial velocities and compositional maps of astronomical objects.
In this paper, we present experimental results from site-selected single quantum dots that have
undergone a number of intermixing process steps via rapid thermal annealing. We show that the
intermixing process blueshifts the dot's emission spectrum without affecting the linewidth as well as
decreasing its biexciton binding energy and s-p shell spacing. The anisotropic exchange splitting is
shown to have undergone a sign inversion implying that the splitting had gone through zero.
Intermixing provides another nanoengineering tool for the design of scalable solid-state photon and
entangled photon pair sources.
Optoelectronic devices based on single, self-assembled semiconductor quantum dots are attractive for applications
in secure optical communications, quantum computation and sensing. In this paper we show how it is possible
to dictate the nucleation site of individual InAs/InP quantum dots using a directed self-assembly process, to
control the electronic structure of the nucleated dots and also how to control their coupling to the optical field by
locating them within the high field region of a photonic crystal nanocavity. For application within fiber networks,
these quantum dots are targeted to emit in the spectral region around 1550 nm.