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The modal dispersion of waveguides typically limits integrated photonic devices to operation with a single polarization state. In this work, we propose a generic mode separation technique we call “interferometric mode splitting” (IMS), which enables guided modes to be separated over wide bandwidths with a large extinction ratio. To demonstrate the general principle of IMS, we show that an unmodified thermally driven silicon photonic Fourier transform spectrometer exhibits a polarization-separating effect in the frequency domain, even though only one polarization-insensitive detector is used. Using this effect, we experimentally demonstrate a simple on-chip spectrometer capable of extracting two-polarization spectra over a wide 1480–1630 nm bandwidth with a greater than 20 dB polarization extinction ratio. These specifications would be highly challenging to achieve using existing, conventional on-chip polarization-splitting techniques. Though we focus on this specific realization of IMS, we also show that IMS is general to various on-chip spectrometer architectures, other spatial modes, and technologies other than thermally driven Fourier transform spectrometers. Interferometric mode splitting shows promise as a general approach for robust and fundamentally broadband detection of orthogonal modes in guided-wave sensing. 

Chalcogenide phase-change materials exhibit large, reversible index shifts that promise nonvolatile, energy-efficient photonic technologies. Yet, current implementations either rely on ultrathin, lossy films integrated with passive Si/SiN waveguides, limiting index modulation, or exploit direct laser writing for localized switching, at the expense of strong optical confinement. Here we demonstrate an antimony trisulfide (Sb₂S₃) waveguide platform where the material itself forms the guiding core. The proposed architecture theoretically supports substantial modulation of both effective index and absorption, thereby providing a robust platform for the realization of reconfigurable and densely integrated photonic devices. 

Abstract Phase‐sensitive integrated photonic devices are highly susceptible to minor manufacturing deviations, resulting in significant performance inconsistencies. This variability has limited the scalability and widespread adoption of these devices. Here, a major advancement is achieved through continuous‐wave (CW) visible light (405 and 520 nm) trimming of plasma‐enhanced chemical vapor deposition (PECVD) silicon‐rich nitride (SRN) waveguides. The demonstrated method achieves precise, bidirectional refractive index tuning with a single laser source in CMOS‐compatible SRN samples with refractive indices of 2.4 and 2.9 (measured at 1550 nm). By utilizing a cost‐effective setup for real‐time resonance tracking in micro‐ring resonators, the resonant wavelength shifts as fine as 10 pm are attained. Additionally, a record red shift of 49.1 nm and a substantial blue shift of 10.6 nm are demonstrated, corresponding to refractive index changes of approximately 0.11 and −2 × 10⁻². The blue and red shifts are both conclusively attributed to thermal annealing. These results highlight SRN's exceptional capability for permanent optical tuning, establishing a foundation for stable, precisely controlled performance in phase‐sensitive integrated photonic devices. 

An energy/area-efficient low-cost broadband linearity enhancement technique using the hybrid of notch-filter and bandpass-filter micro-ring modulators (Hybrid-MRMs) is proposed to achieve higher than 3.01-dB improvement in spurious-free-dynamic-ranges with intermodulation distortions (dSFDRIMD) and 17.9-dB improvement in integral nonlinearity (dINLPP) over a conventional notch-filter MRM (NF-MRM) across a 4.8-dB extinction-ratio full-scale range based on rapid silicon-photonics fabrication results for the emerging applications of various analog and digital optical communication systems. 

The advent of chirped-pulse amplification in the 1980s and femtosecond Ti:sapphire lasers in the 1990s enabled transformative advances in intense laser–matter interaction physics. Whereas most of experiments have been conducted in the limited near-infrared range of 0.8–1 μm, theories predict that many physical phenomena such as high harmonic generation in gases favor long laser wavelengths in terms of extending the high-energy cutoff. Significant progress has been made in developing few-cycle, carrier-envelope phase-stabilized, high-peak-power lasers in the 1.6–2 μm range that has laid the foundation for attosecond X ray sources in the water window. Even longer wavelength lasers are becoming available that are suitable to study light filamentation, high harmonic generation, and laser–plasma interaction in the relativistic regime. Long-wavelength lasers are suitable for sub-bandgap strong-field excitation of a wide range of solid materials, including semiconductors. In the strong-field limit, bulk crystals also produce high-order harmonics. In this review, we first introduce several important wavelength scaling laws in strong-field physics, then describe recent breakthroughs in short- (1.4–3 μm), mid- (3–8 μm), and long-wave (8–15 μm) infrared laser technology, and finally provide examples of strong-field applications of these novel lasers. Some of the broadband ultrafast infrared lasers will have profound effects on medicine, environmental protection, and national defense, because their wavelengths cover the water absorption band, the molecular fingerprint region, as well as the atmospheric infrared transparent window.