Integrated Multimode Waveguide With Photonic Lantern for Speckle Spectroscopy

We propose a high-resolution compact spectrometer based on a multimode waveguide (MMW) integrated with a planar photonic lantern (PL). Four modes were launched into the MMW via asymmetric directional couplers (ADCs) and individually switched by four modulators. The mode field of the MMW was spatially sampled by four separate detectors. Measurement of the 64 possible states (16 switch states x 4 modes) allowed the spectrum of the optical signal to be recovered. Experimentally, we demonstrated spectral correlation width of 0.16-nm in the measurement at 1560 nm using a MMW with 0.5 mm length for both sparse and continuous spectra retrieval. To scale up, the spectrometer resolution can be estimated by delta lambda = lambda(2)/Delta n(eff) L while the operational bandwidth can be estimated to be 2(N) x N x delta lambda, with N denoting the number of modes supported in the whole system. This work may lead to ultra-compact and high-resolution spectrometer systems.

Automated summary

A high-resolution compact spectrometer based on a multimode waveguide integrated with a planar photonic lantern is proposed in the study, showing potential for ultra-compact and high-resolution spectrometer systems. The system demonstrated spectral correlation width of 0.16-nm at 1560 nm and can scale up for wider operational bandwidth by estimating the spectrometer resolution and the number of supported modes.