VCSELs for Optical Communications and Sensing

Dear Colleagues,

In the last decades, vertical-cavity surface emitting lasers (VCSELs) have gained great attention in optical communication systems thanks to their intrinsic advantages, such as low production costs, energy efficiency, easy 2-D integration for mass production and small footprint. In particular, thanks to their sub-mA threshold currents and bandwidths in excess of 20 GHz, VCSELs find wide applications as optical sources in optical transmitters both for Datacom and telecom networks based on simple intensity modulation/direct detection (IM/DD) in the short (850 nm) and long (1310/1550 nm) wavelength regions. However, the continuous growth of bandwidth demand in Datacom networks, needed to provide distributed computing and cloud-based services, and in optical access/metro networks, to support different data traffic including mobile backhaul/fronthaul and the migration towards a more flexible, efficient and agile paradigm, are posing new challenges, urgently requiring very high-bandwidth, low-cost and power-efficient solutions. Advanced modulation formats based on IM/DD or coherent detection in combination with digital signal processing and coding will play an important role in future optical communications networks, as they enable an increase of spectral efficiency and reduced lane count and thus cost and power dissipation.

VCSEL exploitation is not limited to optical communication systems. In fact, their intrinsic characteristics like wide free-spectral range, circular beam shape and large and continuous tuning make them interesting for gas sensing, optical coherence tomography, fiber Bragg-grating sensing, and light ranging applications. Many sensing/measurement applications require coherence, spectral purity and/or the capability to focus the beam to a diffraction-limited spot, implying that single-mode VCSELs are needed. In addition, polarization stability has to be maintained under variations of current and temperature, since polarization switching leads to reduced coherence and spectral broadening. Moreover, some sensing (and other) applications require wide and precise tuning of the VCSEL emission wavelength. Movable top mirrors could be integrated using micro-electrical-mechanical systems (MEMS) technology, leading to tens of nm tuning ranges with side-mode suppression ratios higher than 40 dB.

The aim of this Special Issue is to gather the most recent developments and applications of VCSEL technology, including but not being limited to the following aspects:

• Theoretical, simulative and experimental analysis of innovative short- and long-wavelength VCSELs and their applications;
• High-bandwidth VCSEL sources for future optical communication systems based on intensity modulation and/or advanced modulation formats;
• Second/third-window VCSELs for optical access/metro network scenarios;
• Long-wavelength VCSELs for sensing;
• Novel energy- and cost-effective photonics technologies for Datacom networks;
• Tunable VCSEL sources for communications and sensing.

Dr. Alberto Gatto
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• Short- and long-wavelength VCSEL modelling
• High-bandwidth VCSELs for advanced optical communication systems
• Datacom and telecom networks based on VCSEL sources
• Wide tunable VCSELs for communication and sensing
• Sensing applications for innovative VCSEL sources
• Polarization stability and coherence for sensing applications
• Energy- and cost-effective photonics technologies