Selective spectral detection of continuum terahertz radiation

Abstract

The knowledge of THz continuum spectra is essential to investigate the emission mechanisms by high energy particle acceleration processes. Technical challenges appear for obtaining selective spectral sensing in the far infrared range to diagnose radiation produced by solar flare burst emissions measured from space as well as radiation produced by high energy electrons in laboratory accelerators. Efforts are been carried out intended for the development of solar flare high cadence radiometers at two THz frequencies to operate outside the terrestrial atmosphere (i.e. at 3 and 7 THz). One essential requirement is the efficient suppression of radiation in the visible and near infrared. Experimental setups have been assembled for testing (a) THz transmission of "low-pass" filters: rough surface mirrors; membranes Zitex G110G and TydexBlack; (b) a fabricated 2.4 THz resonant grid band-pass filter transmission response for polarization and angle of incidence; (c) radiation response from distinct detectors: adapted commercial microbolometer array using HRFZ-Si window, pyroelectric module and Golay cell; qualitative detection of solar radiation at a sub-THz frequency has been tested with a microbolometer array placed at the focus of the 1.5 m reflector for submillimeter waves (SST) at El Leoncito, Argentina Andes.

Cross-Shaped Terahertz Metal Mesh Filters: Historical Review and Results

“…In Kaufmann et al [17], different filters at 2.4 THz have been fabricated using THz semitransparent materials as substrate. In this work, it is compared the transmission profile obtained by a suspended metal mesh, a filter on a TydexBlack base, and by a metal mesh sandwiched between TPX layers.…”

SUB-THz AND Hα ACTIVITY DURING THE PREFLARE AND MAIN PHASES OF AGOESCLASS M2 EVENT

“…This means that the antenna temperatures corrected for the source angular displacements with respect to the beams are independent of the accuracy of the pointing of the cluster of beams on the solar disk. The absolute uncertainty of the location of the cluster of the sub-THz beams on the solar disk is known to be better that 0.5 arc minutes (Kaufmann et al 2010). This uncertainty is represented by the length of the cross arms in Figure 1, indicating a burst position at one time.…”

“…Hα observations were obtained at "Bernard Lyot" Solar Observatory, Campinas, SP, Brazil (Marcon 2009). The 0.2 and 0.4 THz observations were obtained by the Solar Submillimeter Telescope (SST), San Juan, Argentina (Kaufmann et al, 2010). Microwave observations were obtained at several frequencies by USAF RSTN monitoring network (Guidice, 1979) and by high sensitivity 7 GHz polarimeter observations at Itapetinga, Atibaia, Brazil (Kaufmann 1971;Correia et al 1999).…”

Metal mesh filters based on Ti, ITO and Cu thin films for terahertz waves

“…The initial observation was made on silver, gold, and chromium films at optical frequencies (Kimand and Choi 2006). Subsequent to the theoretical studies and experimental efforts, researchers started to investigate on producing several types of filters which show high-transmission peaks lying in the range 100 GHz up to 14 THz and with the property of bandpass widths between 13 up to 50 % of the central frequency (Ma et al 2009;Kaufmann et al 2010;Winnewiser et al 1999). In the bandpass geometry of the metal mesh filters, the conventional filter is the cross-shaped type in which the dimensions of the cross width (J), length (K), and periodicity (G) determine the frequency profile.…”