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Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators

Nagarjun, KP and Selvaraja, Shankar Kumar and Supradeepa, VR (2016) Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators. In: Conference on Silicon Photonics XI, FEB 15-17, 2016, San Francisco, CA.

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Official URL: http://dx.doi.org/10.1117/12.2208668

Abstract

High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

Item Type: Conference Proceedings
Additional Information: Copy right for this article belongs to the SPIE-INT SOC OPTICAL ENGINEERING, 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA
Department/Centre: ?? OS-CNSE ??
Depositing User: Id for Latest eprints
Date Deposited: 28 Oct 2016 07:32
Last Modified: 28 Oct 2016 07:32
URI: http://eprints.iisc.ac.in/id/eprint/55183

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