We present upgrades to the visible-light (600nm to 800 nm) high-contrast imaging polarimeter, VAMPIRES, installed on the Subaru Coronagraphic Extreme Adaptive Optics instrument (SCExAO). These upgrades included low read noise, high dynamic range qCMOS detectors, a novel dichroic-based multiband imaging optic for spectral differential imaging, a suite of classic Lyot coronagraphs, and an achromatic fast polarization modulator. VAMPIRES is capable of diffraction-limited imaging (17 mas to 22 mas angular resolution) and achieves Strehl ratios up to ∼60% with 5σ coronagraphic contrast of 10-4 at 0.1′′ and 10-6 at >0.4′′. We highlight commissioning results from HD 169142, R Aqr, Neptune, and HD 1160B.
One of the primary goals of HgCdTe linear-mode avalanche photodiode arrays is to provide a 1kx1k pixels format, @15 μm pitch, near-infrared (0.9 to 2.5 μm) detector suitable for ultra-low background astronomical applications and long integration times. Such science goals impose very strict detector requirements, namely a dark current <0.001 [e−/pix/sec] and a sub-electron read noise. The Institute for Astronomy (IfA), University of Hawaii has partnered with Leonardo Company to develop such devices, using fine control of the photodiode process to enable noise-free amplification of the charge carriers and a readout circuit optimized for minimal glow. We discuss the first results of the tests conducted at the IfA on this new device operated in our cryogenic testbed. We report the values of dark current, read noise and conversion gain, as well as its cosmetic qualities that we have measured at a temperature of 50K. The measured dark current of these devices at low bias voltages is of ∼3 [e-/pix/ksec] (ksec=1000 seconds). We show that this dark current is dominated by the glow emitted by the ROIC of the detector when it is being read out. The intrinsic dark current of these devices is consistent with zero, with a best estimate of ∼0.1 [e-/pix/ksec]. The glow coming from the ROIC is measured to be ∼0.08 [e-/pix/frame], or 1 [e-/pix] every ∼12 frames. The read noise of these devices starts around ∼10 [e-/pix/frame] at a bias voltage of 3V, and decreases by a factor of 1.3 with each +1V increment of the bias voltage, in agreement with theory. It is reduced to ∼2 [e-/pix/frame] at a bias voltage of 8V.
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