Seong-sik Min

The Sydney‐AAO Multi‐object Integral field spectrograph

We demonstrate a novel technology that combines the power of the multi-object spectrograph with the spatial multiplex advantage of an integral field spectrograph (IFS). The SydneyAAO (Australian Astronomical Observatory) Multi-object IFS (SAMI) is a prototype widefield system at the Anglo-Australian Telescope (AAT) that allows 13 imaging fibre bundles (‘hexabundles’) to be deployed over a 1-degree diameter field of view. Each hexabundle comprises 61 lightly fused multi-mode fibres with reduced cladding and yields a 75 per cent filling factor. Each fibre core diameter subtends 1.6 arcsec on the sky and each hexabundle has a field of view of 15 arcsec diameter. The fibres are fed to the flexible AAOmega double-beam spectrograph, which can be used at a range of spectral resolutions (R = λ/δλ ≈ 1700–13 000) over the optical spectrum (3700–9500 A). We present the first spectroscopic results obtained with SAMI for a sample of galaxies at z ≈ 0.05. We discuss the prospects of implementing hexabundles at a much higher multiplex over wider fields of view in order to carry out spatially resolved spectroscopic surveys of 10 4 –10 5 galaxies.

First Science with SAMI: A Serendipitously Discovered Galactic Wind in ESO 185-G031

We present the first scientific results from the Sydney-AAO Multi-Object IFS (SAMI) at the Anglo-Australian Telescope. This unique instrument deploys 13 fused fiber bundles (hexabundles) across a one-degree field of view allowing simultaneous spatially resolved spectroscopy of 13 galaxies. During the first SAMI commissioning run, targeting a single galaxy field, one object (ESO 185-G031) was found to have extended minor axis emission with ionization and kinematic properties consistent with a large-scale galactic wind. The importance of this result is twofold: (1) fiber bundle spectrographs are able to identify low surface brightness emission arising from extranuclear activity and (2) such activity may be more common than presently assumed because conventional multi-object spectrographs use single-aperture fibers and spectra from these are nearly always dominated by nuclear emission. These early results demonstrate the extraordinary potential of multi-object hexabundle spectroscopy in future galaxy surveys.

A new family of 2-D wavelength-time spreading code for optical code-division multiple-access system with balanced detection

We propose a new family of 2¿D wavelength-hopping/ time-spreading code for optical code-division multiple-access systems with balanced detection, and we numerically analyze the characteristics of the proposed system. By using the proposed decoding scheme, the undesired interference is efficiently eliminated. The proposed scheme has the enhanced performance and allows for a large number of simultaneous users compared with the 3-D and other balanced codes for differential detection.

Demonstration of uniform multicore fiber Bragg gratings

Fiber Bragg gratings in multicore fibers have significant potential as compact and robust filters for research and commercial applications. With the aid of an innovative, flat-fielded Mach-Zehnder interferometer, we demonstrate deep (>30 dB) narrow (100 pm at 3 dB; 90 pm at 10 dB) notches in the outer 6 cores of a 7-core fiber at a constant wavelength ( ± 15 pm). This is a crucial step in the development of FBGs operating within multimode fibers that carry an arbitrary number of spatial modes.

High-power figure-of-eight fiber laser with passive sub-ring loops for repetition rate control

The operation of an erbium figure-of-eight all-fiber laser with a fundamental repetition rate of 5.68 MHz, peak power of 0.7 kW and pulse width of 420 fs is reported. Four times the fundamental repetition rate is achieved with two passive sub-ring loops at a repetition rate of 22.8 MHz. The sub-ring loop consists of only a single-mode fiber coupler with an input port and output port connected so as to make the time delay an odd multiple half-period of the input pulse period. This method is simple and inexpensive when compared with conventional methods employing sub-ring cavity or special fiber Bragg grating to control repetition rate.

Multi-core fiber Bragg grating developments for OH suppression

We discuss the development of multi-core fiber Bragg gratings (FBGs) to be applied to astrophotonics, more specifically to near-infrared spectroscopy for ground-based instruments. The multi-core FBGs require over 100 notches to reject the OH lines in a broad wavelength range (160 nm). The number of cores of the fiber should correspond to the mode number in the multi-mode fibers and should be large enough to be able to capture a sufficient amount of light from the telescope. A phase-mask based technique is used to fabricate the multi-core FBGs.

Spatial dispersion in three-dimensional drawn magnetic metamaterials

We characterize spatial dispersion in longitudinally invariant drawn metamaterials with a magnetic response at terahertz frequencies, whereby a change in the angle of the incident field produces a shift in the resonant frequency. We present a simple analytical model to predict this shift. We also demonstrate that the spatial dispersion is eliminated by breaking the longitudinal invariance using laser ablation. The experimental results are in agreement with numerical simulations.

Design and analysis of spatially variant microlens-array diffuser with uniform illumination for short-range infrared wireless communications using photometric approach

A microlens-array was designed to transform the Gaussian radiation pattern of a point source to the uniform illumination in the far field, which can be used as an optical diffuser of short-range infrared wireless communication systems, allowing a transmitter to use more optical power safely. This paper describes how to design such a microlens-array diffuser and investigates the property of the light distribution generated thereby.

Semiconductor optical amplifier based high duty-cycle, self-starting figure-eight 1.7 GHz laser source

The operation of a self-starting, passively harmonic modelocked, figure-eight laser is experimentally demonstrated. A stable pulse train with near half duty-cycle is produced at a repetition rate of 1.7 GHz at 1536 nm wavelength without any starting/triggering mechanism and stays modelocked as long as it is being pumped.

Time-wavelength hybrid optical CDMA system with tunable encoder/decoder using switch and fixed delay-line

Abstract A novel tunable encoding/decoding scheme based on an arrayed waveguide grating (AWG) and optical switches for time–wavelength hybrid (TWH) optical code division multiple-access (CDMA) systems is proposed. The scheme uses optical switches and fixed delay lines instead of tunable delay lines (TDLs) and utilizes the structure of the TWH optical signature sequences. The advantages of the scheme are that it can be implemented using fewer elements and that the encoded signal suffers lower loss than in those using TDLs. A TWH optical CDMA system for local area network (LAN) applications using the proposed tunable encoder and a simple fixed decoder is examined and its feasibility is experimentally verified.