Color centers in silicon carbide have increasingly attracted attention in recent years owing to their excellent properties such as single photon emission, good photostability, and long spin coherence time even at room temperature. As compared to diamond which is widely used for

| In this paper, we present a brief history of silicon photonics from the early research papers in the late 1980s and early 1990s, to the potentially revolutionary technology that exists today. Given that other papers in this special issue give detailed reviews of key aspects of the technology, this paper will concentrate on the key technological milestones that were crucial in demonstrating the capability of silicon photonics as both a successful technical platform, as well as indicating the potential for commercial success. The paper encompasses discussion of the key technology areas of passive devices, modulators, detectors, light sources, and system integration.In so doing, the paper will also serve as an introduction to the other papers within this special issue.

Abstract:The majority of the most successful optical modulators in silicon demonstrated in recent years operate via the plasma dispersion effect and are more specifically based upon free carrier depletion in a silicon rib waveguide. In this work we overview the different types of free carrier depletion type optical modulators in silicon. A summary of some recent example devices for each configuration is then presented together with the performance that they have achieved. Finally an insight into some current research trends involving silicon based optical modulators is provided including integration, operation in the mid-infrared wavelength range and application in short and long haul data transmission links.

Quantum sensors with solid state electron spins have attracted considerable interest due to their nanoscale spatial resolution. A critical requirement is to suppress the environment noise of the solid state spin sensor. Here we demonstrate a nanoscale thermometer based on silicon carbide (SiC) electron spins. We experimentally demonstrate that the performance of the spin sensor is robust against dephasing due to a self-protected mechanism from the intrinsic transverse electric field of the defect. The SiC thermometry may provide a promising platform for sensing in a noisy environment, e.g. biological system sensing.Nanoscale thermometry has been demonstrated based on various of systems like quantum dot 1,2 , nanoparticle 3,4 , NV (nitrogen vacancy) center spin in diamond 1,6-8 due to its significant benefits to microelectronics and bio-application 910 . Recently, electron spins in silicon carbide have been found to be optically addressable and show superior coherence properties 11,1213 . Besides the favorable features of both CMOS and biocompatibility, sillicon carbide provides a large number of types defects that can be used as candidates for a spin sensor, including PL1-PL6 in 4H-SiC 12 ,QL1-QL6 in 6H-SiC 11 and Ky5 in 3C-SiC 14 . As compared with quantum dot and NV center, nanoscale and highly sensitive thermometry based on a semiconductor material silicon carbide maybe more fascinating because of its versatility in production and widely application in the realm of electronic devices 15 . Moreover, unlike NV center which has 4 possible orientations in bulk diamond 16 , one type of divacancy spins in silicon carbide has the same orientation which improves the sensitivity in varies of sensing application by using an ensemble of divacancy spins.One main challenge for quantum sensors is to improve the sensitivity of quantum metrology against environment noise. Several methods have been developed such as spin echo, dynamical decoupling 17,1819 and quantum error correction 20,21 . These active methods usually make experiments more involved and suffer from certain limitations. In this Letter, we demonstrate high sensitivity temperature sensing based on the electron spins in 4H-SiC divacancies. Especially, the transverse electric field in such defects can suppress the effect of longitudinal magnetic field noise, leading to an improved sensitivity. The self-protected mechanism against decoherence provides an appealing route for scenarios where active methods for suppressing noise may not be suitable.Theory -Here we are considering PL5 defect in SiC 12 , which is a basal C 1h symmetry divacancy showing high optically detected magnetic resonance (ODMR) contrast at room temperature 12 . The ground state shows a spin-1 character with the basis written as {| ↑ , |0 , | ↓ }. The three ground states split at zero magnetic field, resulting in two ODMR resonance spectrum at D + E and D − E. The spin Hamiltonian can be written aswhereFor H 0 term, D(T ) is the temperature-dependence zero field splitting, E x is the transverse el...

Water radical cations, the crucial intermediates in many aqueous reactions and biochemical processes, are difficult to be experimentally investigated due to its short lifetime and low abundance. Herein, a homemade device based on energy-tunable discharge was employed to deposit suitable amounts of energy to atmospheric pressure pure water vapor for abundant production of water radical cations, which were stabilized as (H 2 O) n +• (n=2-5) with the maximal abundance (≥ 8.3×10 6 cps) for (H 2 O) 2 +• as characterized by mass spectrometry (MS).The abundance of water radical cations was optimized by adjusting the experimental parameters such as discharge voltage (2.5 kV), temperature of the MS inlet (140 o C), carrier gas flow (20 mL/min) and the distance between the discharge tip and the MS inlet (12 mm). The ambient formation of water radical cations was further confirmed by the high reactivity of the as-prepared water radical cations, which instantly reacted with benzene, ethyl acetate and dimethyl disulfide, showing rich chemistry with the ionic and radical characters. Moreover, the computations confirm that the O-O single-electron bound dimer (B) as well as the hydronium hydroxyl radical complex (A) accounts for the unusual chemistry of the water radical cations, providing a facile approach to access the high reactivity of water radical cations under the ambient condition.