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			<titleStmt><title level='a'>Interferometric modal splitting enables broadband, dual-polarization on-chip spectroscopy</title></titleStmt>
			<publicationStmt>
				<publisher>OPTICA</publisher>
				<date>12/22/2025</date>
			</publicationStmt>
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				<bibl> 
					<idno type="par_id">10679098</idno>
					<idno type="doi">10.1364/OPTICA.577600</idno>
					<title level='j'>Optica</title>
<idno>2334-2536</idno>
<biblScope unit="volume">13</biblScope>
<biblScope unit="issue">1</biblScope>					

					<author>Karl Johnson</author><author>Vladimir Fedorov</author><author>Dmitrii Belogolovskii</author><author>Andrew Grieco</author><author>Noah A Rubin</author><author>Yeshaiahu Fainman</author>
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			<abstract><ab><![CDATA[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 1480–1630nm bandwidth with a greater than 20dB 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.]]></ab></abstract>
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