For modern color-rendering applications, efficient blue, green, and red LEDs are required. While efficient green and red perovskite LEDs have been demonstrated, blue devices lag significantly behind due to the poor quality of chloride-based perovskites. Here, we show that doping manganese into blue perovskite nanocrystals increases their brightness and efficiency. By putting doped nanocrystals into LEDs, we see a 4-fold increase in efficiency, demonstrating that blue LEDs can be as efficient as their red and green cousins.

Photonic crystal nanobeam cavities are versatile platforms of interest for optical communications, optomechanics, optofluidics, cavity QED, etc. In a previous work [1], we proposed a deterministic method to achieve ultrahigh Q cavities. This follow-up work provides systematic analysis and verifications of the deterministic design recipe and further extends the discussion to air-mode cavities. We demonstrate designs of dielectric-mode and air-mode cavities with Q > 10 9 , as well as cavities with both high-Q (> 10 7 ) and high on-resonance transmissions (T > 95%).

A deterministic design of an ultrahigh Q, wavelength scale mode volume photonic crystal nanobeam cavity is proposed and experimentally demonstrated. Using this approach, cavities with Q> 10 6 and on-resonance transmission T>90% are designed. The devices fabricated in Si and capped with low-index polymer, have Q=80,000 and T=73%. This is, to the best of our knowledge, the highest transmission measured in deterministically designed, wavelength scale high Q cavities.Photonic crystal (PhC) The large computational cost, in particular the computation time, needed to perform the simulation of high-Q cavities make this trial based method inefficient. Inverse engineering design, in which the physical structure is optimized by constructing specific target functions and constraints, was also proposed[14] [15]. A design recipe based on the desired field distribution is proposed in [16]. In this letter, we propose and experimentally demonstrate a deterministic method to design an ultrahigh Q, sub-wavelength scale mode volume, PhC nanobeam cavity( Figure.1) that is strongly coupled to the feeding waveguide(i.e. near unity on resonance transmission). The design approach is deterministic in the sense that it does not involve any trial-based hole shifting, re-sizing and overall cavity re-scaling to ensure ultra-high Q cavity. Moreover, the final cavity resonance has less than 2% deviation from a predetermined frequency. Our design method requires only computationally inexpensive, photonic band calculations (e.g. using plane wave expansion method), and is simple to implement.The Q factor of a PhC nanobeam cavity can be maximized by reducing the out-of plane scattering(Q sc ) due to the coupling to the radiation modes. As shown previously [3][16], scattered power (P sc ) can be expressed as an integral of spatial fourier frequencies within a light cone, calculated over the surface above the cavity:. The integral is minimized when major fourier components are tightly localized (in k-space) at the edge of the first Brillioun zone [4]. We start by considering the ideal field distribution on this surface which would minimize P sc . A general property of these nanobeam cavities is that it consists of the waveguide region of length L, that sup- * Electronic address: quan@fas.harvard.edu ports propagating modes, surrounded by infinitely long Bragg mirror on each side( Figure.1a). Without the loss of generality, we consider the TE-like cavity mode with Hz as a major field component. In the case of conventional periodic Bragg mirror, evanescent field inside the mirror can be expressed as sin(β Bragg x) exp(−κx), where κ is attenuation constant. The cavity field inside the waveguide region can be represented as sin(β wg x). As mentioned above, scattering loss decreases in mirror section when β Bragg = π/a, while phase matching between mirror and waveguide [7], β Bragg = β wg , minimizes the scattering loss at cavity-mirror interface. The spatial fourier transform of such cavity field is approximately a Lorentzian in the vicinity of π/a. As ...

A variety of nanoscale photonic, mechanical, electronic, and optoelectronic devices require scalable thin film fabrication. Typically, the device layer is defined by thin film deposition on a substrate of a different material, and optical or electrical isolation is provided by the material properties of the substrate or by removal of the substrate. For a number of materials this planar approach is not feasible, and new fabrication techniques are required to realize complex nanoscale devices. Here, we report a three-dimensional fabrication technique based on anisotropic plasma etching at an oblique angle to the sample surface. As a proof of concept, this angled-etching methodology is used to fabricate free-standing nanoscale components in bulk single-crystal diamond, including nanobeam mechanical resonators, optical waveguides, and photonic crystal and microdisk cavities. Potential applications of the fabricated prototypes range from classical and quantum photonic devices to nanomechanical-based sensors and actuators.

Single-crystal diamond, with its unique optical, mechanical and thermal properties, has emerged as a promising material with applications in classical and quantum optics. However, the lack of heteroepitaxial growth and scalable fabrication techniques remains the major limiting factors preventing more wide-spread development and application of diamond photonics. In this work, we overcome this difficulty by adapting angled-etching techniques, previously developed for realization of diamond nanomechanical resonators, to fabricate racetrack resonators and photonic crystal cavities in bulk single-crystal diamond. Our devices feature large optical quality factors, in excess of 10 5 , and operate over a wide wavelength range, spanning visible and telecom. These newly developed high-Q diamond optical nanocavities open the door for a wealth of applications, ranging from nonlinear optics and chemical sensing, to quantum information processing and cavity optomechanics.