We report on the demonstration of three-dimensional optical trapping inside the core of a hollow-core microstructured optical fiber specifically designed and fabricated for this purpose. Optical ...trapping was achieved by means of an external tweezers beam incident transversely on the fiber and focused through the fiber cladding. Trapping was achieved for a range of particle sizes from 1 to 5 µm, and manipulation of the particles in three-dimensions through the entire cross-section of the fiber core was demonstrated. Spectroscopy was also performed on single fluorescent particles, with the fluorescence captured and guided in the fiber core. Video tracking methods allowed the optical traps to be characterized and photobleaching of single particles was also observed and characterized.
We demonstrate a 3x1 fiber-based photonic lantern spatial-multiplexer with mode-selectivity greater than 6 dB and transmission loss of less than 0.3 dB. The total insertion loss of the mode-selective ...multiplexers when coupled to a graded-index few-mode fiber was < 2 dB. These mode multiplexers showed mode-dependent loss below 0.5 dB. To our knowledge these are the lowest insertion and mode-dependent loss devices, which are also fully compatible with conventional few-mode fiber technology and broadband operation.
Twin-hollow-core microstructured optical fibres have been fabricated and characterised for the first time. The fibre cladding structure results in guidance by the inhibited coupling mechanism, in ...which there is a low overlap between the core modes and surrounding structure. This results in minimal interaction between the modes of each core in the transmission bands of the fibre and hence minimal coupling between the cores. It is shown that light is able to couple between the cores via coupling to cladding struts in the high loss wavelength bands.
Single Mode, Extreme Precision Doppler Spectrographs Schwab, Christian; Leon-Saval, Sergio G.; Betters, Christopher H. ...
Proceedings of the International Astronomical Union,
08/2012, Volume:
8, Issue:
S293
Journal Article
Peer reviewed
Open access
The ‘holy grail’ of exoplanet research today is the detection of an earth-like planet: a rocky planet in the habitable zone around a main-sequence star. Extremely precise Doppler spectroscopy is an ...indispensable tool to find and characterize earth-like planets; however, to find these planets around solar-type stars, we need nearly one order of magnitude better radial velocity (RV) precision than the best current spectrographs provide. Recent developments in astrophotonics (Bland-Hawthorn & Horton 2006, Bland-Hawthorn et al. 2010) and adaptive optics (AO) enable single mode fiber (SMF) fed, high resolution spectrographs, which can realize the next step in precision. SMF feeds have intrinsic advantages over multimode fiber or slit coupled spectrographs: The intensity distribution at the fiber exit is extremely stable, and as a result the line spread function of a well-designed spectrograph is fully decoupled from input coupling conditions, like guiding or seeing variations (Ihle et al. 2010). Modal noise, a limiting factor in current multimode fiber fed instruments (Baudrand & Walker 2001), can be eliminated by proper design, and the diffraction limited input to the spectrograph allows for very compact instrument designs, which provide excellent optomechanical stability. A SMF is the ideal interface for new, very precise wavelength calibrators, like laser frequency combs (Steinmetz et al. 2008, Osterman et al. 2012), or SMF based Fabry-Perot Etalons (Halverson et al. 2013). At near infrared wavelengths, these technologies are ready to be implemented in on-sky instruments, or already in use. We discuss a novel concept for such a spectrograph.
Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires ...that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.
ABSTRACT
Focal Ratio Degradation (FRD) in optical fibres can result in light loss. In astronomical instrumentation, FRD must be controlled because light levels are low. A new Integral Field ...Spectrograph (IFS) instrument called Hector, was recently completed and was installed on the Anglo-Australian Telescope (AAT) in Australia in 2021 December. The integral field units (IFUs) for Hector made with hexagonally packed multi-mode fibres are called hexabundles. In this paper, we introduce a cone-beam measurement method to measure FRD at optical wavelengths. We present the FRD and throughput performance of the hexabundles for Hector and show that the process for making hexabundles introduced no additional significant FRD beyond that of the bare fibre.
The majority of optical fiber technology developments in the applied sciences have arisen from developments in telecommunications. However, the photonic lantern is one of several devices that arose ...to solve problems in astronomy. Interestingly, these devices are now being extensively used in multimode optical telecommunications research and are likely to find commercial use in the next few years. A photonic lantern allows for a low-loss transformation of a multimode system into a discrete number of single-mode ones and vice versa, thus, enabling their use as mode multiplexers/demultiplexers in Space Division Multiplexing (SDM). Further, it provides seamless integration with the rest of single-mode photonic technologies in telecommunication systems. In this paper, we will discuss the theory and function of the photonic lantern, along with several different variants of the technology needed for their use in SDM communications, focusing on the fiber-bundle photonic lanterns type. We will also discuss some of its current and future applications.
In astronomy and related fields there is a pressing need to efficiently inject light, transmitted through the atmosphere, into a single-mode fibre. However this is extremely difficult due to the ...large, rapidly changing aberrations imprinted on the light by the turbulent atmosphere. An adaptive optics system must be used, but its effectiveness is limited by non-common-path aberrations and insensitivity to certain crucial modes. Here we introduce a new concept device - the hybrid mode-selective photonic lantern - which incorporates both focal plane wavefront sensing and broadband single-mode fibre injection into a single photonic package. The fundamental mode of an input multimode fibre is directly mapped over a broad (1.5 to 1.8 μ m) bandwidth to a single-mode output fibre with minimal (<0.1%) crosstalk, while all higher order modes are sent to a fast detector or spectrograph for wavefront sensing. This will enable an AO system optimised for maximum single-mode injection, sensitive to otherwise ‘blind’ modes and avoiding non-common-path wavefront-sensor aberrations.
PDF
