Fiber-Coupled Diamond Micro-Waveguides toward an Efficient Quantum Interface for Spin Defect Centers

Abstract

We report the direct integration and efficient coupling of nitrogen vacancy (NV) color centers in diamond nanophotonic structures into a fiber-based photonic architecture at cryogenic temperatures. NV centers are embedded in diamond micro-waveguides (μWGs), which are coupled to fiber tapers. Fiber tapers have low-loss connection to single-mode optical fibers and hence enable efficient integration of NV centers into optical fiber networks. We numerically optimize the parameters of the μWG-fiber-taper devices designed particularly for use in cryogenic experiments, resulting in 35.6% coupling efficiency, and experimentally demonstrate cooling of these devices to the liquid helium temperature of 4.2 K without loss of the fiber transmission. We observe sharp zero-phonon lines in the fluorescence of NV centers through the pigtailed fibers at 100 K. The optimized devices with high photon coupling efficiency and the demonstration of cooling to cryogenic temperatures are an important step to realize fiber-based quantum nanophotonic interfaces using diamond spin defect centers.

Diamond quantum thermometry: From foundations to applications

“…Nitrogen and group-IV colour defect centres in diamond, including nitrogen-, silicon-, germanium-, tin-, and lead-vacancy centres (NV, SiV, GeV, SnV, and PbV), exhibit distinct optical and spin properties that can be used for various quantum applications, such as the development of single photon sources [60][61][62][63][64][65], quantum gates [66,67], quantum memories [68,69], and quantum sensors [70,71].…”

A narrow-band sodium-resonant fiber-coupled single photon source

“…An alternative way of coupling the emission of solidstate quantum emitters to the guided modes of a fiber is through coupling to the evanescent field of a tapered fiber. This has been demonstrated with a variety of emitters such as quantum dots [4][5][6], nitrogen vacancy centers in diamond [2,[7][8][9], defects in hexagonal boron nitride [10], and also molecules [11]. Nevertheless, coupling to tapered fibers is difficult as the fibers easily get contaminated, break, or lose transmission when being cooled down.…”

A fiber-integrated nanobeam single photon source emitting at telecom wavelengths

“…Several previous works have reported fiber-coupled single photon sources using either semiconductor quantum dots [20][21][22][23][24][25][26][27][28] or nitrogen-vacancy centers in diamond [29][30][31][32][33] .…”