Abstract
We describe and experimentally demonstrate a method for active control of resonant modulators and filters in an integrated photonics platform. Variations in resonance frequency due to manufacturing processes and thermal fluctuations are corrected by way of balanced homodyne locking. The method is compact, insensitive to intensity fluctuations, minimally disturbs the micro-resonator, and does not require an arbitrary reference to lock. We demonstrate long-term stable locking of an integrated filter to a laser swept over 1.25 THz. In addition, we show locking of a modulator with low bit error rate while the chip temperature is varied from 5 to 60° C.
Highlights
Integrated optical micro-resonators have been investigated for a wide range of applications, including micro-ring modulators [1,2,3] and filters, Kerr frequency comb generation [4] and even nano-opto-mechanical systems (NOMS) [5]
We developed a wavelength control scheme based on balanced homodyne detection that is suitable for filters and modulators, is insensitive to intensity fluctuations, does not disturb the optical signal or resonator and requires only the simplest control electronics, which are readily fabricated in modern CMOS nodes [22]
The balanced detector, which generates the error signal, Y(β), used for locking, differences the photocurrents of the two output ports of the Mach-Zehnder Interferometer (MZI), and is described by Eq (3), where α is the responsivity of the photodetectors, G is the transimpedance gain, n/2Z0 is a constant representing the conversion from field amplitude to average optical power in the waveguide and am is the effective mode area
Summary
Integrated optical micro-resonators have been investigated for a wide range of applications, including micro-ring modulators [1,2,3] and filters, Kerr frequency comb generation [4] and even nano-opto-mechanical systems (NOMS) [5]. The self-heating of the optical beam can significantly tune the resonant wavelength of the resonator in a bistable manner [7] It is typically very difficult, if not impossible, to precisely fabricate a silicon micro-resonator to a given wavelength channel [8,9]. We developed a wavelength control scheme based on balanced homodyne detection that is suitable for filters and modulators, is insensitive to intensity fluctuations, does not disturb the optical signal or resonator and requires only the simplest control electronics, which are readily fabricated in modern CMOS nodes [22]
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