[
    {
        "id": "thesis:18973",
        "collection": "thesis",
        "collection_id": "18973",
        "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11042026-000045209",
        "primary_object_url": {
            "basename": "Chen_P_1999.pdf",
            "content": "final",
            "filesize": 67808267,
            "license": "other",
            "mime_type": "application/pdf",
            "url": "/18973/1/Chen_P_1999.pdf",
            "version": "v2.0.0"
        },
        "type": "thesis",
        "title": "Terahertz Generation via Optical-Heterodyne Conversion: Development of a New Far-Infrared Spectrometer and Its Applications toward a Better Understanding of Nonrigid, Astronomically Important Molecules",
        "author": [
            {
                "family_name": "Chen",
                "given_name": "Pin",
                "orcid": "0000-0003-1195-9666",
                "clpid": "Chen-Pin"
            }
        ],
        "thesis_advisor": [
            {
                "family_name": "Blake",
                "given_name": "Geoffrey A.",
                "orcid": "0000-0003-0787-1610",
                "clpid": "Blake-G-A"
            }
        ],
        "thesis_committee": [
            {
                "family_name": "Bercaw",
                "given_name": "John E.",
                "clpid": "Bercaw-J-E"
            },
            {
                "family_name": "Blake",
                "given_name": "Geoffrey A.",
                "orcid": "0000-0003-0787-1610",
                "clpid": "Blake-G-A"
            },
            {
                "family_name": "Okumura",
                "given_name": "Mitchio",
                "orcid": "0000-0001-6874-1137",
                "clpid": "Okumura-M"
            },
            {
                "family_name": "Pickett",
                "given_name": "Herbert M.",
                "clpid": "Pickett-H-M"
            },
            {
                "family_name": "Zewail",
                "given_name": "Ahmed H.",
                "clpid": "Zewail-A-H"
            }
        ],
        "local_group": [
            {
                "literal": "div_chem"
            }
        ],
        "abstract": "<p>Generation of far-infrared radiation via terahertz optical heterodyne conversion (TOHC) has been implemented in high-resolution spectroscopic applications. Using this newly\r\ndeveloped spectrometer technology, spectroscopic investigations of NH3 in the excited v2 state and H20 in the ground and excited v2 states were conducted.</p>\r\n<p>To overcome the linewidth problems associated with using diode lasers as heterodyne pump sources, optical feedback techniques were employed to develop a compact, narrow-linewidth, and tunable source of THz radiation for far-infrared spectroscopy. Distributed-Bragg-reflector (DBR) semiconductor lasers at 850 nm pump a low-temperature-grown GaAs (LTG-GaAs) photomixer. Resonant optical feedback\r\nstabilizes the center frequencies and narrows the linewidths of the DBR lasers. The heterodyne linewidth (full-width at half-maximum) of two optically locked DBR lasers was reduced from 40 MHz to 50 kHz on the 20-ms timescale and from 90 MHz to 2 MHz on the 10-s timescale. To demonstrate spectroscopic capabilities, fully resolved rotational spectra of acetonitrile near 312 GHz were acquired. The detection limit was 1 x 10<sup>-4</sup> Hz<sup>-1/2</sup> (noise/total power).</p>",
        "doi": "10.7907/hjyq-0z05",
        "publication_date": "1999",
        "thesis_type": "phd",
        "thesis_year": "1999"
    }
]