We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.The ability to map magnetic field distributions with high sensitivity and nanoscale resolution is of crucial importance for fundamental studies ranging from material science to biology, as well as for the development of new applications in spintronics and quantum technology [1][2][3]. In that context, an ideal scanning probe magnetometer should provide quantitative magnetic field mapping at the nanoscale under ambient conditions. In addition, the magnetic sensor should not introduce a significant magnetic perturbation of the probed sample.Over the last decades, different roads have been taken towards ultra-sensitive detection of magnetic fields including superconducting quantum interference devices (SQUIDs) [1], semiconductor-based Hall probes [1] and optical magnetometers [2]. Even though extremely high sensitivity has been achieved with these devices, their spatial resolution remains limited at the micron-scale. Prominent approaches to reach nanoscale resolution are scanning-tunneling microscopy [4], mechanical detection of magnetic resonance [5], nanoSQUIDs [6], X-ray microscopy [7] and magnetic force microscopy (MFM) [8]. Since the latter technique operates under ambient conditions without any specific sample preparation, it is now routinely used for mapping magnetic field gradients around magnetic nanostructures. However, besides introducing an inevitable perturbation of the studied magnetic sample owing to the intrinsic magnetic nature of the probe [7], MFM does not provide quantitative information about the magnetic field distribution.Here we follow a recently proposed approach to magnetic sensing based on optically detected electron spin resonance (ESR) [10]. It was shown that this method applied to a single nitrogen-vacancy (NV) defect in diamond could provide an unprecedented combination of spatial resolution and magnetic sensitivity under ambient conditions [6,11,12,14]. The principle of the measurement * Electronic address: vjacques@lpqm.ens-cachan.fr is similar to the one used in optical magnetometers based on the precession of spin-polarized atomic gases [2]. The applied magnetic field is evaluated by measuring the Zeeman shifts of the NV defect spin sublevels. In this article we demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the ESR frequency of a single NV defect placed at the apex of ...
The scalability of a quantum network based on semiconductor quantum dots lies in the possibility of having an electrical control of the quantum dot state as well as controlling its spontaneous emission. The technological challenge is then to define electrical contacts on photonic microstructures optimally coupled to a single quantum emitter. Here we present a novel photonic structure and a technology allowing the deterministic implementation of electrical control for a quantum dot in a microcavity. The device consists of a micropillar connected to a planar cavity through one-dimensional wires; confined optical modes are evidenced with quality factors as high as 33,000. We develop an advanced in-situ lithography technique and demonstrate the deterministic spatial and spectral coupling of a single quantum dot to the connected pillar cavity. Combining this cavity design and technology with a diode structure, we demonstrate a deterministic and electrically tunable single-photon source with an extraction efficiency of around 53±9%.
We present an interferometric displacement sensor based on a folded low-finesse Fabry-Perot cavity. The fiber-optic sensor uses a quadrature detection scheme based on the wavelength modulation of a DFB laser. This enables measuring position changes over a range of 1 m for velocities up to 2 m/s. The sensor is well suited to work in extreme environments such as ultrahigh vacuum, cryogenic temperatures, or high magnetic fields and supports multichannel applications. The interferometer achieves a repeatability of 0.44 nm(3σ) at a working distance of 20 mm, a resolution of 1 pm, and an accuracy of 1 nm.
A compact sensor head combining optical interference and scanning probe microscopy in a single instrument has been developed. This instrument is able to perform complementary quantitative measurements, combining fast nondestructive three-dimensional surface analysis with high lateral resolution imaging. A custom interference microscope sensor head has been designed as the optical microscope objective and integrated within the architecture of a commercial interference microscope. The combined instrument makes available both the acquisition software and the hardware interface of the commercial microscope. The latter is able to function as a phase-shift interferometer or white light interferometer. Furthermore, the use of an optical fiber to transmit light from an external laser: (i) removes a major heat source from the measurement environment and (ii) makes aperture correction unnecessary. The lateral resolution of the instrument has been extended by the addition of a previously developed compact scanning probe microscope (SPM) module to the custom interference microscope objective. This SPM unit is based upon piezoresistive cantilever technology. The “piezolevers” are self-sensing and therefore require no additional systems, such as optical beam deflection or fiber interferometry, to monitor their displacement. The mechanical simplicity of the piezolever SPM unit allows for a small physical size and can thus be added to the custom optical sensor head without violating constraints on the working distance defined by the optics. A major benefit of the system, in terms of a quantitative nanometrology, is the possibility to perform a traceable and direct calibration of the SPM module. This calibration is achieved practically by measuring an appropriate sample at a common location using both techniques. Results are presented here for the measurement of two calibration standards and a test sample to demonstrate the increased lateral resolution of the instrument.
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