Abstract – Optical sensing at long wavelengths presents significant opportunities and significant challenges. The longwave infrared and terahertz ranges are renowned for their potential to sense molecules in a variety of contexts, such as high-speed chemical imaging, disease detection, and environmental monitoring; however, their promise has yet to be fulfilled due to a lack of compact broadband sources and low-loss integrated photonics platforms. The most important sensing challenges require extremely wideband sources to achieve specificity and selectivity, but to date, there are no technologies that are compact, bright, and broadband. I will discuss some of the work of my group that seeks to address this challenge. First, I will discuss our development of quantum cascade laser-based frequency combs, light sources that fill the gap between broadband incoherent sources and lasers. I will also discuss how our experimental investigations of these combs led to my discovery of a new fundamental comb state that manifests in almost any laser at any wavelength, acting as the phase equivalent of passive modelocking , . Next, I will discuss our recent development of ultra-low-loss platforms for long wavelengths based on hybrid photonic integration, which allowed us to create optical resonators in the longwave infrared with quality factors 100 times better than the state-of-the-art , . This approach is fully wavelength-scalable and allows for the first efficient nonlinear optics at long wavelengths, serving as a foundational element for future applications in quantum sensing. Finally, I will discuss our development of ptychoscopy, a new sensing modality that allows for ultra-precise measurements of optical spectra. This measurement enables the measurement of remote signals with quantum-limited frequency resolution over the entire bandwidth of a comb, for the first time allowing incoherent spectra to be characterized with the precision techniques of combs . D. Burghoff, “Unraveling the origin of frequency modulated combs using active cavity mean-field theory,” Optica, vol. 7, no. 12, pp. 1781–1787, Dec. 2020. M. Roy, Z. Xiao, S. Addamane, and D. Burghoff, “Fundamental scaling limits and bandwidth shaping of frequency-modulated combs.” (in press, Optica) D. Ren, C. Dong, S. J. Addamane, and D. Burghoff, “High-quality microresonators in the longwave infrared based on native germanium,” Nat. Commun., vol. 13, no. 1, Art. no. 1, Oct. 2022. D. Ren et al., “Low-loss hybrid germanium-on-zinc selenide waveguides in the longwave infrared,” Nanophotonics, Jan. 2024. D. J. Benirschke, N. Han, and D. Burghoff, “Frequency comb ptychoscopy,” Nat. Commun., vol. 12, no. 1, p. 4244, Jul. 2021. Co-sponsored by: Advanced Science Research Center - the Graduate Center - City University of New York Speaker(s): David Burghoff Room: Auditorium, Bldg: Advanced Science Research Center CUNY, 85 St. Nicholas Terrace, New York, New York, United States, NY 10031, Virtual: https://events.vtools.ieee.org/m/447317