Multi-wavelength holography with a single spatial light modulator for ultracold atom experiments

The authors acknowledge funding from the Leverhulme Trust Research Project Grant RPG-2013-074 and from the EPSRC grant GR/T08272/01.We demonstrate a method to independently and arbitrarily tailor the spatial profile of light of multiple wavelengths and we show possible applications to ultracold atoms experiments. A single spatial light modulator is programmed to create a pattern containing multiple spatially separated structures in the Fourier plane when illuminated with a single wavelength. When the modulator is illuminated with overlapped laser beams of different wavelengths, the position of the structures is wavelength-dependent. Hence, by designing their separations appropriately, a desired overlap of different structures at different wavelengths is obtained. We employ regional phase calculation algorithms and demonstrate several possible experimental scenarios by generating light patterns with 670 nm, 780 nm and 1064 nm laser light which are accurate to the level of a few percent. This technique is easily integrated into cold atom experiments, requiring little optical access.PostprintPeer reviewe

Measurement of variations in gas refractive index with 10-9 resolution using laser speckle

Funding: This work was supported by funding from the Leverhulme Trust (RPG-2017-197) and the UK Engineering and Physical Sciences Research Council (EP/P030017/1).Highly-resolved determination of refractive index is vital in fields ranging from biosensing through to laser range-finding. Laser speckle is known to be a sensitive probe of the properties of the light and the environment, but to date speckle-based refractive index measurements have been restricted to 10^-6 resolution. In this work we identify a strategy to optimise the sensitivity of speckle to refractive index changes, namely by maximising the width of the distribution of optical path lengths in the medium. We show that this can be realised experimentally by encapsulating the medium of interest within an integrating sphere. We demonstrate that variations of the refractive index of air as small as 4.5x10-9 can be resolved with an uncertainty of 7x10-10. This is an improvement of three orders of magnitude when compared to previous speckle-based methods.Publisher PDFPeer reviewe

Speckle-based determination of the polarisation state of single and multiple laser beams

Funding: Leverhulme Trust (RPG-2017-197); UK Engineering and Physical Sciences Research Council (EP/P030017/1).Laser speckle is generated by the multiple interference of light through a disordered medium. Here we study the premise that the speckle pattern retains information about the polarisation state of the incident field. We analytically verify that a linear relation exists between the Stokes vector of the light and the resulting speckle pattern. As a result, the polarisation state of a beam can be measured from the speckle pattern using a transmission matrix approach. We perform a quantitative analysis of the accuracy of the transmission matrix method to measure randomly time-varying polarisation states. In experiment, we find that the Stokes parameters of light from a diode laser can be retrieved with an uncertainty of 0.05 using speckle images of 150$\times$150 pixels and 17 training states. We show both analytically and in experiment that this approach may be extended to the case of more than one laser field, demonstrating the measurement of the Stokes parameters of two laser beams simultaneously from a single speckle pattern and achieving the same uncertainty of 0.05.Publisher PDFPeer reviewe

Measurement of vacuum pressure with a magneto-optical trap : a pressure-rise method

This research was supported by UK EPSRC grant GR/T08272/01, IOP Scotland and the Leverhulme Trust Research Project Grant RPG-2013-074.The lifetime of an atom trap is often limited by the presence of residual background gases in the vacuum chamber. This leads to the lifetime being inversely proportional to the pressure. Here we use this dependence to estimate the pressure and to obtain pressure rate-of-rise curves, which are commonly used in vacuum science to evaluate the performance of a system. We observe different rates of pressure increase in response to different levels of outgassing in our system. Therefore we suggest that this is a sensitive method which will find useful applications in cold atom systems, in particular where the inclusion of a standard vacuum gauge is impractical.Peer reviewe

Feedback-enhanced algorithm for aberration correction of holographic atom traps

We show that a phase-only spatial light modulator can be used to generate non-trivial light distributions suitable for trapping ultracold atoms, when the hologram calculation is included within a simple and robust feedback loop that corrects for imperfect device response and optical aberrations. This correction reduces the discrepancy between target and experimental light distribution to the level of a few percent (RMS error). We prove the generality of this algorithm by applying it to a variety of target light distributions of relevance for cold atomic physics.Comment: 5 pages, 4 figure

Analysis and error model for a two-degrees-of-freedom elastically supported tuned gyro.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1972.Includes bibliographical references.M.S

The influence of socioeconomic deprivation on multimorbidity at different ages: a cross-sectional study

<b>Background</b> Multimorbidity occurs at a younger age in individuals in areas of high socioeconomic deprivation but little is known about the 'typology' of multimorbidity in different age groups and its association with socioeconomic status.<p></p> <b>Aim</b> To characterise multimorbidity type and most common conditions in a large nationally representative primary care dataset in terms of age and deprivation.<p></p> <b>Design and setting</b> Cross-sectional analysis of 1 272 685 adults in Scotland.<p></p> <b>Method</b> Multimorbidity type of participants (physical-only, mental-only, mixed physical, and mental) and most common conditions were analysed according to age and deprivation.<p></p> <b>Results</b> Multimorbidity increased with age, ranging from 8.1% in those aged 25–34 to 76.1% for those aged ≥75 years. Physical-only (56% of all multimorbidity) was the most common type of multimorbidity in those aged ≥55 years, and did not vary substantially with deprivation. Mental-only was uncommon (4% of all multimorbidity), whereas mixed physical and mental (40% of all multimorbidity) was the most common type of multimorbidity in those aged <55 years and was two- to threefold more common in the most deprived compared with the least deprived in most age groups. Ten conditions (seven physical and three mental) accounted for the top five most common conditions in people with multimorbidity in all age groups. Depression and pain featured in the top five conditions across all age groups. Deprivation was associated with a higher prevalence of depression, drugs misuse, anxiety, dyspepsia, pain, coronary heart disease, and diabetes in multimorbid patients at different ages.<p></p> <b>Conclusion</b> Mixed physical and mental multimorbidity is common across the life-span and is exacerbated by deprivation from early adulthood onwards

Overcoming the speckle correlation limit to achieve a fiber wavemeter with attometer resolution

The measurement of the wavelength of light using speckle is a promising tool for the realization of compact and precise wavemeters and spectrometers. However, the resolution of these devices is limited by strong correlations between the speckle patterns produced by closely spaced wavelengths. Here, we show how principal component analysis of speckle images provides a route to overcome this limit. Using this, we demonstrate a compact wavemeter that measures attometer-scale wavelength changes of a stabilized diode laser, eight orders of magnitude below the speckle correlation limit.PostprintPeer reviewe

Can quantum gas microscopes directly image exotic glassy phases?

With the advent of spatially resolved fluorescence imaging in quantum gas microscopes (see e.g. [1]), it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system, and use it to simulate the density distributions seen in single-shot fluorescence microscopy [2]. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments by using spatial light modulators (see [3] and references therein) to tailor the lattice, which will allow further properties of the Bose glass to be measured. References: [1] E Haller, et al., "Single-atom imaging of fermions in a quantum-gas microscope" Nature Physics 11, 738 (2015) [2] S J Thomson, et al., "Measuring the Edwards-Anderson order parameter of the Bose glass: A quantum gas microscope approach" Phys. Rev. A 94, 051601(R) (2016) [3] F Buccheri, et al., "Holographic optical traps for atom-based topological Kondo devices" New J. Phys. 18, 075012 (2016)PostprintNon peer reviewe

Is laser repetition rate important for two-photon light sheet microscopy?

Funding: UK Engineering and Physical Sciences Research Council (EPSRC) - EP/P030017/1.We demonstrate the thermal advantages of using low repetition rate, high peak power lasers for imaging in two-photon light sheet microscopy using a Bessel light beam. We compare the use of two ultrashort pulsed lasers in such an imaging system: a high repetition rate source operating at 80 MHz and a low repetition rate source operating at 1 MHz. The low repetition rate laser requires approximately one order of magnitude lower average power than the high repetition rate source to yield the same fluorescent signal. These lasers are used to image Zebrafish larvae and record their heart rates. The data show heart rate values 30% in excess of the ground truth baseline value when imaged with the high repetition rate source due to deleterious heating, whereas the low repetition rate source yields data only a few percent above this ground truth value.Publisher PDFPeer reviewe