Heterodyne instrumentation upgrade at the Caltech Submillimeter Observatory

Balanced receivers are under development at the Caltech Submillimeter Observatory (CSO) for the 230/460 GHz and 345/660 GHz atmospheric windows. The mixers are tunerless, implemented in a balanced configuration, have a 4-8 GHz IF, and can be used in dual frequency observation mode. As shall be seen, the balanced arrangement provides a high level of amplitude noise immunity and allows all of the available LO power to be used. In turn, this permits complete automation of the receivers by means of synthesized LO source(s). A disadvantage of balanced mixers is, perhaps, that the sidebands at the IF remain convolved (DSB), unlike sideband separating (2SB) receivers. The latter, however are unbalanced and do not have the noise and LO injection advantages of balanced mixers. For the CSO, balanced mixers covering the range 180-720 GHz were judged most promising to facilitate many of the astrophysical science goals in the years to come. In parallel, a dual polarization 280-420~GHz continuous comparison (correlation) receiver is in an advanced state of development. The instrument has two beams on the sky; a reference and a signal beam. Using only cooled reflecting optics, two polarizing grids, and a quadrature hybrid coupler, the sky beams are coupled to four tunerless SIS mixers (both polarizations). The 4-12 GHz mixer IF outputs are, after amplification, correlated against each other. In principle, this technique results in flat baselines with very low RMS noise, and is especially well suited for high redshift Galaxy work. Not only do these changes greatly enhance the spectroscopic capabilities of the CSO, they will also enable the observatory to be integrated into the Harvard-Smithsonian Submillimeter Array (SMA), as an additional telescope

Herschel observations of EXtra-Ordinary Sources: The Terahertz spectrum of Orion KL seen at high spectral resolution

We present the first high spectral resolution observations of Orion KL in the frequency ranges 1573.4 - 1702.8 GHz (band 6b) and 1788.4 - 1906.8 GHz (band 7b) obtained using the HIFI instrument on board the Herschel Space Observatory. We characterize the main emission lines found in the spectrum, which primarily arise from a range of components associated with Orion KL including the hot core, but also see widespread emission from components associated with molecular outflows traced by H2O, SO2, and OH. We find that the density of observed emission lines is significantly diminished in these bands compared to lower frequency Herschel/HIFI bands.Comment: Accepted for publication in the Herschel HIFI special issue of Astronomy and Astrophysics Letters, 5 pages, 3 figure

Search for optical pulsations in PSR J0337+1715

We report on a search for optical pulsations from PSR J0337+1715 at its observed radio pulse period. PSR J0337+1715 is a millisecond pulsar (2.7 ms spin period) in a triple hierarchical system with two white dwarfs, and has a known optical counterpart with g-band magnitude 18. The observations were done with the ARray Camera for Optical to Near-IR Spectrophotometry at the 200 arcsec Hale telescope at Palomar Observatory. No significant pulsations were found in the range 4000–11 000 Å, and we can limit pulsed emission in g band to be fainter than 25 mag

Herschel observations of EXtra-Ordinary Sources (HEXOS): The Terahertz spectrum of Orion KL seen at high spectral resolution

We present the first high spectral resolution observations of Orion KL in the frequency ranges 1573.4–1702.8 GHz (band 6b) and 1788.4–1906.8 GHz (band 7b) obtained using the HIFI instrument on board the Herschel Space Observatory. We characterize the main emission lines found in the spectrum, which primarily arise from a range of components associated with Orion KL including the hot core, but also see widespread emission from components associated with molecular outflows traced by H2O, SO2, and OH. We find that the density of observed emission lines is significantly diminished in these bands compared to lower frequency Herschel/HIFI bands

Herschel observations of EXtra-Ordinary Sources (HEXOS): The present and future of spectral surveys with Herschel/HIFI

We present initial results from the Herschel GT key program: Herschel observations of EXtra-Ordinary Sources (HEXOS) and outline the promise and potential of spectral surveys with Herschel/HIFI. The HIFI instrument offers unprecedented sensitivity, as well as continuous spectral coverage across the gaps imposed by the atmosphere, opening up a largely unexplored wavelength regime to high-resolution spectroscopy. We show the spectrum of Orion KL between 480 and 560 GHz and from 1.06 to 1.115 THz. From these data, we confirm that HIFI separately measures the dust continuum and spectrally resolves emission lines in Orion KL. Based on this capability we demonstrate that the line contribution to the broad-band continuum in this molecule-rich source is ∼20−40% below 1 THz and declines to a few percent at higher frequencies. We also tentatively identify multiple transitions of HD18O in the spectra. The first detection of this rare isotopologue in the interstellar medium suggests that HDO emission is optically thick in the Orion hot core with HDO/H2O ∼ 0.02. We discuss the implications of this detection for the water D/H ratio in hot cores

Demonstration of sub-3 ps temporal resolution with a superconducting nanowire single-photon detector

Improvements in temporal resolution of single-photon detectors enable increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging, and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the most efficient time-resolving single-photon-counting detectors available in the near-infrared, but understanding of the fundamental limits of timing resolution in these devices has been limited due to a lack of investigations into the timescales involved in the detection process. We introduce an experimental technique to probe the detection latency in SNSPDs and show that the key to achieving low timing jitter is the use of materials with low latency. By using a specialized niobium nitride SNSPD we demonstrate that the system temporal resolution can be as good as 2.6 ± 0.2 ps for visible wavelengths and 4.3 ± 0.2 ps at 1,550 nm

Demonstration of sub-3 ps temporal resolution with a superconducting nanowire single-photon detector

Improvements in temporal resolution of single-photon detectors enable increased data rates and transmission distances for both classical and quantum optical communication systems, higher spatial resolution in laser ranging, and observation of shorter-lived fluorophores in biomedical imaging. In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the most efficient time-resolving single-photon-counting detectors available in the near-infrared, but understanding of the fundamental limits of timing resolution in these devices has been limited due to a lack of investigations into the timescales involved in the detection process. We introduce an experimental technique to probe the detection latency in SNSPDs and show that the key to achieving low timing jitter is the use of materials with low latency. By using a specialized niobium nitride SNSPD we demonstrate that the system temporal resolution can be as good as 2.6 ± 0.2 ps for visible wavelengths and 4.3 ± 0.2 ps at 1,550 nm