**Photonic Crystal Waveguides and Plasmonics**

206 Photonic Crystals – Innovative Systems, Lasers and Waveguides

[130] V V Krishnamachari and E O Potma, Interferometric switching of coherent anti-Stokes Raman scattering signals in microscopy, Phys. Rev. A, 2009, 79(1): 013823. [131] K M Hajek, B Littleton, D Turk, et al., A method for achieving super-resolved widefield CARS microscopy, Opt. Express, 2010, 18(18): 19263-19272. [132] W Liu and H B Niu, Diffraction barrier breakthrough in coherent anti-Stokes Raman

Rev. A, 2011, 83(2): 023830.

scattering microscopy by additional probe-beam induced phonon depletion, Phys.

**0**

**11**

Luca Marseglia

*United Kingdom*

**Photonic Crystal Coupled to N-V Center in Diamond**

*and Electronic Engineering, University of Bristol, BS8 1UB*

*Centre for Quantum Photonics, H. H. Wills Physics Laboratory & Department of Electrical*

In this work we aim to exploit one of the most studied defect color centers in diamond , the negatively charged nitrogen vacancy (NV−) color center, a three level system which emits a single photon at a wavelength of 637*nm* providing a possible deterministic single photon emitter very useful for quantum computing applications. Moreover the possibility of placing a NV−in a photonic crystal cavity will enhance the coupling between photons and NV−center. This could also allow us to address the ground state of the NV−center, whose spin, could be used as qubit. It is also remarkable to notice that for quantum computing purposes it is very useful to increase the light collection from the NV−centers, and in order to do that we performed a study of another structure, the solid immersion lens, which consists of an hemisphere whose center is at the position of an emitter, in this case the NV−center, increasing the collection of the light from it. In order to create these structures we used a method called focused ion beam which allowed us to etch directly into the diamond many different kinds of structures. In order to allow an interaction between these structures and the NV−centers we need to have a method to locate the NV−center precisely under the etched structures. We developed a new technique (Marseglia et al. (2011)) where we show how to mark a single NV−center and how to etch a desired structure over it on demand. This technique gave very good results allowing us to etch a solid immersion lens onto a NV−previously located and

characterized, increasing the light collection from the NV−of a factor of 8×.

Diamond has emerged in recent years as a promising platform for quantum communication and spin qubit operations as shown by Gabel et al. (2006), as well as for "quantum imaging" based on single spin magnetic resonance or nanoscopy. Impressive demonstrations in all these areas have mostly been based on the negatively-charged nitrogen vacancy center, NV−, which consists of a substitutional nitrogen atom adjacent to a carbon vacancy. Due to its useful optical and magnetic spin selection properties, the NV−center has been used by Kurtsiefer et al. (2000) to demonstrate a stable single photon source and single spin manipulations (Hanson et al. (2006)) at room temperature. A single-photon source based on NV−in nano-diamond is already commercially available, and a ground state spin coherence time of 15*ms* has been observed in ultra-pure diamond at room temperature. At present, one of the biggest issues preventing diamond from taking the lead among competing technologies

**2. Introduction to Nitrogen Vacancy center in diamond**

**1. Introduction**
