VCSEL-Based Optical Frequency Combs: Toward Efficient Single-Device Comb Generation

Abstract

. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Serrano, A.R.C.; de Dios Fernandez, C.; Cano, E.P.; Ortsiefer, M.; Meissner, P.; Acedo, P., "VCSEL-Based Optical Frequency Combs: Toward Efficient Single-Device Comb Generation", IEEe Photonics Technology Letters, (2013Letters, ( ), 25(20), 1981Letters, ( ,1984 such as Mode-Locking Laser Diodes (MLLD) [7] or microresonators [8]. These devices can be divided according to their repetition frequency, being MLLDs in the order of several GHz, and microresonators in the order of few hundreds of GHz. Microresonators are recent and very promising devices able to generate extremely wide OFCGs, but their high repetition frequencies make them unsuitable for a significant number of applications [8]. On the other hand, MLLDs have been widely used during the last decades, but they still present important drawbacks, like the absence of continuous tunability of the repetition frequency and the need of specially designed structures that nowadays are still far from offering reliability and repeatability in the manufacturing processes for commercial purposes.In this sense, some recent works have recovered a wellknown technique for inducing pulsed operation in a semiconductor laser, Gain-Switching (GS), in order to implement multi-GHz OFCGs that are to overcome some of these drawbacks associated with MLLDs [4], [9]. Although they offer much less optical span than MLLDs, GS-based OFCGs offer wide tunability range, high correlation between optical modes, and low-cost; as they can be implemented using commercial semiconductor lasers. Nevertheless, if standard edge-emitting lasers are used, the amount of direct modulation power needed for an OFCG featuring 8-10 lines is about 0.5-1 W, which makes necessary the use of Radiofrequency (RF) power amplifiers [4], [10]. Moreover, the generated optical spectra are not flat, and additional stages based on nonlinear techniques and comprising several external components are usually needed to obtain flat-topped pulses, such as cascaded Intensity or Phase Electro-Optical Modulators (EOMs) [11][12][13] and Four Wave Mixing (FWM) [14].For this reason, different types of semiconductor lasers have been used under GS regime in the search of compact, commercial devices based pulsed sources, and, Vertical Cavity Surface Emitting Lasers (VCSELs) are promising candidates [15][16][17][18][19]. VCSELs need very few current to operate (under 10 mA), and their integration capabilities as well as the capacity for on-chip testing allow for low cost optical subsystems with an excellent energy efficiency. Moreover, they have demonstrated wide wavelength tuning capabilities (in excess of 100 nm) with direct control of the cavity length using membranes [20]. In this sense, VCSELs would lead to ...

Experimental Study of VCSEL-Based Optical Frequency Comb Generators

“…A degradation of the phase noise of this beat tone is associated to an overall loss of coherence among the optical modes. In [7] we found that the phase noise of the VCSEL based GS-OFCG is similar to that of the reference signal. In the present work (Figure 4) we have evaluated EO and Combined techniques.…”

“…The use of edge emitting technologies such as Fabry-Perot [10], Distributed Feedback Bragg lasers or Discrete Mode [11] has been recently reported. In this sense, our previous work [7] shows that the use of high performance Vertical Cavity Surface Emitting Lasers (VCSEL) permits the generation of an enhanced comb, record in energy efficiency and optical span. This result drives our interest to study the possibilities of this technology as the core of an OFCG that could meet the requirements detailed before.…”

“…The maturity of commercially available LD would benefit the resulting OFCG taking it from the laboratory to the application field in a reliable and cost efficient way. Several techniques have already demonstrated promising results [7], [8]. They can be grouped in direct or indirect techniques.…”

“…When the GS regime is induced, the injected RF power into the laser is P RF,GS = 15dBm and the bias current is I bias = 11.4mA at f RF = 5GHz. These working conditions were chosen in order to offer the best OFCG performance [7].…”

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

“…Possibilities if simplifying the expansion was also discussed. In 2013, A. R. Criado et al [215] reported on the use of VCSEL for gain switched comb generation. The authors reported on the generation of a comb exhibiting 20 tones within a 3 dB ripple at a FSR of 6.25 GHz.…”