The technique of using magnetic-tape recorders and atomic frequency standards to operate two widely separated radio telescopes as a phase-coherent interferometer when the stations have no radio-frequency connecting link has been successfully tested at the National Research Council of Canada's Algonquin Radio Observatory.

Abstract:We report the development of a fiber-integrated picosecond source at 560 nm by second harmonic generation of a Raman fiber laser. A picosecond ytterbium master oscillator power fiber amplifier is used to pulse-pump a Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode operating at 1120 nm. The pulse train generated at 1120 nm is frequency-doubled in a fiber-coupled periodicallypoled lithium niobate crystal module, producing 450 mW of average power at 560 nm with a pulse duration of 150 ps at a repetition rate of 47.5 MHz. The near diffraction-limited (M 2 = 1.02) collimated output beam is ideal for super-resolution microscopy applications.

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This paper presents the development of a Raman fiber amplifier optical source with a maximum output power of 1.1 W centered around 1651 nm, and its application in miniaturized 3D printed photoacoustic spectroscopy (PAS) trace gas sensing of methane. The Raman amplifier has been constructed using 4.5 km of dispersion shifted fiber, a 1651 nm DFB seed laser and a commercial 4W EDFA pump. The suppression of stimulated Brillouin scattering (SBS) using a high frequency modulation of the seed laser is investigated for a range of frequencies, leading to an increase in optical output power of the amplifier and reduction of its noise content. The amplifier output was used as the source for a miniature PAS sensor by applying a second modulation to the seed laser at the resonant frequency of 15.2 kHz of the miniature 3D printed gas cell. For the targeted methane absorption line at 6057 cm -1 the sensor system performance and influence of the SBS suppression is characterized, leading to a detection limit (1σ) of 17 ppb methane for a signal acquisition time of 130 s, with a normalized noise equivalent absorption coefficient of 4.1·10 -9 cm -1 W Hz -1/2 for the system.Index Terms-Miniaturized fiber optic sensor, 3D printed photoacoustic trace gas sensor, Raman fiber amplifier system, SBS suppression

Abstract. A new type of radio telescope is proposed which may make very large telescopes more affordable. The telescope is considered to be one of several identical elements that form a synthesis array. It is composed of an almost flat primary reflector that is slightly adjustable in shape and made up of identical square flat panels supported by the ground. A very long focal length imposes the unusual condition that the receiver be carried by an airborne vehicle such as a powered, helium-filled balloon. The position of the balloon is measured and controlled as accurately as possible and residual errors in the balloon's position are dealt with in two ways. Errors of a few metres are corrected by moving the receiver feed point electronically. Larger errors are corrected by adjusting the primary reflector so as to move its focal point to follow the balloon. These features maintain telescope efficiency and correct pointing so long as the balloon lies anywhere within a large volume surrounding its ideal position. The problem of controlling the balloon position is thereby substantially eased. The telescope has the wide sky coverage needed for synthesis observations and an estimated optimum diameter in the range 100 to 300 m. It will operate from decimetre to short centimetre wavelengths, or, with smaller panels, millimetre wavelengths.

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We report the development of a fully fiber-integrated pulsed master oscillator power fibre amplifier (MOPFA) source at 780 nm, producing 3.5 W of average power with 410 ps pulses at a repetition rate of 50 MHz. The source consists of an intensity modulated 1560 nm laser diode amplified in an erbium fiber amplifier chain, followed by a fiber coupled periodically poled lithium niobate crystal module for frequency doubling. The source is then used for generating visible light through four-wave mixing in a length of highly nonlinear photonic crystal fiber: 105 mW at 668 nm and 95 mW at 662 nm are obtained, with pump to anti-Stokes conversion slope efficiencies exceeding 6% in both cases.