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Wavelength division multiplex (WDM) passive optical network (PON) is considered for converged fixed mobile broadband access networking. We propose to utilize low-cost tunable lasers at the remote sites, together with a centralized wavelength locker. Practical implementations require a transparently added downstream signaling channel and upstream per-channel pilot tones for channel tagging and remote wavelength control. We demonstrate, for the first time, 26-Gbps discrete multitone transmission modulated on a low-cost wide tunable vertical surface emitting laser over up to 40 km of standard single-mode fiber. The results confirm that converged fixed mobile WDM-PON systems based on low-cost lasers carrying discrete multitone modulation are a technically viable approach.

We demonstrate 84-Gb/s four-level pulse amplitude modulation (PAM-4) over up to 1.6-km standard single mode fiber using a 20-GHz single mode short cavity vertical cavity surface emitting laser diode at a transmission wavelength of 1525 nm. Different equalizer approaches including a common feedforward equalizer, a nonlinear Volterra equalizer (NLVE), a maximum likelihood sequence estimator (MLSE) and their combinations are evaluated working either as an equalizer for a standard PAM-4 or a partial response PAM-4 signal with seven levels. It is demonstrated that a standard FFE is not enough for a transmission distance of >0.6 km, while the use of an NLVE or FFE + MLSE is able to improve the transmission distance towards 1 km. The use of partial-response PAM-4 FFE in combination with a short memory MLSE is able to efficiently equalize the bandwidth limitations, showing more than 10-times BER improvement compared to standard NLVE or FFE + MLSE at a transmission distance of 1.6 km. Using a partial-response NLVE instead of an PR-FFE further performance improvement is achieved, resulting in BERs below the KP4 FEC-threshold with a BER-limit of 2E-4 after 1.6-km transmission distance, allowing error free operation.

We propose and experimentally demonstrate the use of a novel-design long-wavelength VCSEL with high direct-modulation speed to implement 40-Gb/s transmission suitable for optical interconnects and short-reach scenarios. The single-mode operation, together with the use of a common optical bandpass filter, enables a fiber reach in the kilometer range. The VCSEL is characterized and directly modulated at 40 Gb/s with a power consumption of 18.5 mW. Bit-error-rate (BER) performance has been analyzed for a pseudorandom bit sequence (PRBS) of length $2^{7}-1$ as commonly done in most of similar studies, as well as for increasing the PRBS lengths up to $2^{31}-1$ to understand the system limitations when applying more realistic data, so as to induce slower dynamics physical effects such as thermal effects. BER values below common forward error correction threshold are measured without an optical amplification up to 1 km of a single-mode fiber. In particular, error-free operation ( $\text {BER} with 1.6 dB of penalty with respect to the back-to-back case was measured for the PRBS length of $2^{7}-1$ .

We demonstrate a 1530 nm VCSEL that can operate error-free without DSP or FEC to 56 Gb/s. At 50 Gb/s, error-free operation is attained up to 2 km of SMF. A two-tap FFE driver is used to precompensate the response of the VCSEL. The optical spectrum of the VCSEL under equalization at 50 Gb/s is analyzed and the chirp properties are reported. The low latency of FEC-free NRZ and the distance of 2 km makes these technology suitable for optical links in both high performance computing and large data centers.

We demonstrate the generation and transmission of a 28-Gb/s intensity modulated optical signal over single mode fiber (SMF) links up to 1, 2, 5, and 10 km employing a 18-GHz 3-dB bandwidth monolithic vertical-cavity surface-emitting laser (VCSEL) based on buried tunnel junction technology with regrown n -doped InP material. Inexpensive technologies such as nonreturn-to-zero on–off keying modulation format, direct detection as well as digital signal processing-based receivers make the transmission feasible for chromatic dispersion (CD) uncompensated SMF links up to 10 km at the 7% hard-decision (HD) forward error correction (FEC) limit. Three different equalizers for the receiver side are investigated in this paper in terms of performance optimization, i.e., the maximum likelihood sequence estimation equalizer (MLSE), the feed-forward equalizer (FFE) and a hybrid scheme that comprises of an FFE and an MLSE equalizer (FFE/MLSE) in cascaded form. Our experimental results indicate that MLSE scheme outperforms the other two counterparts in all transmission scenarios. Performance optimization in terms of MLSE complexity is also presented. Less complex implementations like FFE equalizer can provide reliable transmission below the 7% HD-FEC limit for links up to 5 km. The FFE/MLSE scheme provides similar performance as MLSE for links up to 5 km, while its performance deteriorates for 10 and 15 km links as signal distortion due to CD becomes too severe to recover the signal. A timing recovery unit is employed before the equalizers in order to compensate for phase offsets and improve the signal quality. Our proposed scheme proves a promising candidate to enable VCSEL-based short reach optical interconnects in data centers and metro-access area.

We demonstrate direct modulation of a widely tunable microelectromechanical system (MEMS) vertical-cavity surface-emitting laser (VCSEL). The wavelength tuning is realized with electrothermal actuation of a SiO $_x$ /SiN $_y$ -based MEMS distributed Bragg reflector (DBR). The DBR is deposited in a low-temperature plasma-enhanced chemical vapor deposition chamber on a InP-based half-VCSEL by means of surface micromachining. More than 60 nm of mode-hop free continuous tuning with a center wavelength of 1554 nm is achieved. A maximum 3-dB small-signal modulation response ( $S_{21}$ ) bandwidth of 7.05 GHz is reported. Quasi-error-free operation of a back-to-back link is demonstrated at 10 Gb/s for a record 47-nm tuning range, showing the compatibility of the MEMS tunable VCSEL as a cost-effective optical source in access networks and interconnects.

We demonstrate a 56 Gb/s four-level pulse-amplitude modulation (PAM-4) transmission using direct detection and a long-wavelength 18-GHz bandwidth vertical-cavity surface-emitting laser as directly modulated light source for short-reach inter- and intra-connects in datacenters and short-reach networks. Error-free transmission over 2 km at 7% hard-decision forward-error correction threshold is achieved by applying powerful equalization schemes at the receiver side. Three equalization schemes, i.e., a maximum likelihood estimation (MLSE), a feed-forward equalizer (FFE), and a combination of the FFE and the MLSE are thoroughly investigated, and the performance comparison between them is carried out.

In this work, we have used a tunable VCSEL for high-speed optical data transmission. To obtain wide tunability, a MEMS-DBR is surface micromachined onto a short-cavity high-speed VCSEL operating at 1550 nm. Ultra-wide continuous tuning is realized with electro-thermal actuation of the MEMS with built-in stress gradient within SiOx/SiNy dielectric layers. The MEMS-VCSEL operates in single-mode with SMSR > 40 dB across the entire tuning range. Quasi-error-free transmission of direct-modulation at record 15 Gbps is reported for 20 nm tuning, showing the potential towards the standard requirements for the SFP+ modules in the tail-ends of the WDM transmission system.

We demonstrate an IQ modulator by employing two monolithic injection-locked VCSELs which are driven to produce pure amplitude modulation. QPSK signals are produced at 10 GBaud with a peak-to-peak modulation voltage of 600 mV.

VCSEL links typically require multiple supply voltages for high-speed and low-power operation. We report a 40-Gb/s 1.5-μm VCSEL link achieving 8.7 pJ/bit of energy efficiency with a 0.13-μm SiGe VCSEL driver and TIA operated at 2.5 V.

We report full C-band tunable, 10 Gbit/s capability, directly modulated MEMS-VCSEL for next generation converged mobile fronthaul and backhaul applications. Bit error rates below 10(-9) were achieved over up to 40 km SSMF.

Optical frequency combs generators (OFCGs) have demonstrated to be extremely useful tools in a wide variety of applications. The current research trends look toward compact devices that are able to offer high phase correlation between optical lines, and in this sense, mode-locked laser diodes (MLLDs), with repetition frequencies in the few gigahertz (GHz) range, and especially microresonators, with repetition frequencies of hundreds of GHz, are the most promising devices fulfilling these requirements. Nevertheless, focusing in the few GHz frequency rate, MLLDs cannot provide continuous tunability and require special devices that are still far from offering reliability and repeatability for commercial use. In this letter, we demonstrate for the first time the generation of a flat OFCG based on a single commercial vertical cavity surface emitting laser under gain-switching regime with 20 optical lines (spaced by 4.2 GHz) in a 3-dB bandwidth, offering wide tunability range and very high phase correlation between optical modes. This OFCG does not need any external modulator and it is the most energy-efficient OFCG reported to date. Publicado

The present experimental work studies the dynamics of dual-polarization optical frequency combs (OFCs) based on gain switching (GS) vertical-cavity surface-emitting laser (VCSEL) diodes under optical injection locking (OIL). This study presents two main results. First, we have obtained an overall comb formed by two orthogonally polarized sub-combs with comparable span and power. The overall comb shows enhanced optical span and flatness and high coherence between its modes. The second result is that we have been able to control the polarization state of the overall comb by tuning the polarization state of the injected light by locking the same single teeth of the comb. This produces an overall comb with single polarization that is parallel or orthogonal. These are novel findings that provide for the development of efficient and compact OFCs based on GS VCSEL sources with versatile polarization dynamics. Ministerio de Economía y Competitividad (MINECO) (RTC 2014 2661 7, TEC2014-52147-R).

Poster of: 2016 Conference on Lasers and Electro-Optics (CLEO), San Jose, CA, USA, 5-10 June 2016 We show, to our knowledge, the broadest VCSEL-based optical frequency comb of 1THz in 20dB span, with 193teeth, obtained by cascading two expansion stages, one with two EO Modulators and the second based on HNLF

We experimentally demonstrate 56-Gbps optical interconnection over 1 km SSMF by using 10G 1550nm VCSEL. PAM4 and Poly-PAM4 MLSE algorithms are developed to optimize the system performance and overcome the chirp-chromatic-dispersion induced power degradation after 1 km fiber transmission.

A novel method for fabricating a single mode optical interconnection platform is presented. The method comprises the miniaturized assembly of optoelectronic single dies, the scalable fabrication of polymer single mode waveguides and the coupling to glass fiber arrays providing the I/O's. The low cost approach for the polymer waveguide fabrication is based on the nano-imprinting of a spin-coated waveguide core layer. The assembly of VCSELs and photodiodes is performed before waveguide layers are applied. By embedding these components in deep reactive ion etched pockets in the silicon substrate, the planarity of the substrate for subsequent layer processing is guaranteed and the thermal path of chip-to-substrate is minimized. Optical coupling of the embedded devices to the nano-imprinted waveguides is performed by laser ablating 45 degree trenches which act as optical mirror for 90 degree deviation of the light from VCSEL to waveguide. Laser ablation is also implemented for removing parts of the polymer stack in order to mount a custom fabricated connector containing glass fiber arrays. A demonstration device was built to show the proof of principle of the novel fabrication, packaging and optical coupling principles as described above, combined with a set of sub-demonstrators showing the functionality of the different techniques separately. The paper represents a significant part of the electro-photonic integration accomplishments in the European 7th Framework project "Firefly" and not only discusses the development of the different assembly processes described above, but the efforts on the complete integration of all process approaches into the single device demonstrator.

In this study, we detail our experimental study on the expansion of vertical-cavity surface-emitting laser (VCSEL) optical frequency combs (OFCs) with different nonlinear techniques. For this purpose, we modulate a VCSEL device under gain switching (GS) regime to obtain an initial seed comb record in terms of energy efficiency and mode coherence. This seed OFC will be improved adding a nonlinear stage to expand this primary signal. The nonlinear techniques here presented are high nonlinear fibers, nonlinear optical loop mirrors, and electro optical phase modulators. In this study, we show the different extended OFCs that these techniques offer and we present a detailed comparison of their characteristics, evaluating the advantages and disadvantages of each technique. We have observed that the obtained OFCs maintain the high coherence offered by the seed VCSEL-OFC. Nevertheless, the optical span, flatness, frequency tunability, dynamic range, energy, and cost efficiency or compactness of each expanded OFC significantly vary, depending on the expansion technique used. Our careful evaluation will serve as a reference to evaluate the suitability of each expansion technique depending on the needs or the application. The authors would like to thank VERTILAS for providing the VCSELs, Luz Wavelabs S.L. for their technical support.

In this work we carry out a experimental study on the polarization properties of a Vertical-Cavity Surface-Emitting Laser (VCSEL) working under Gain Switching (GS) regime and the characteristics of the resulting optical frequency comb signal. We have observed that each of the two polarization modes presented in the VCSEL Continuous Wave (CW) emission spectrum generate a separate Optical Frequency Comb (OFC) whose modes are phase correlated thanks to the GS regime. We study how these combs associated to the main and orthogonal polarization modes respectively vary depending on the input parameters to the VCSEL (bias current and radiofrequency power and frequency). The correlation between both OFCs in the best operation point as defined by the OFC characteristics is also evaluated. Therefore, this work demonstrates that two orthogonally polarized combs are generated that exhibit a high correlation between each other that combine to produce a wider overall optical comb. Hence, we can predict the feasibility of dual-polarization VCSEL-based Optical Frequency Comb Generators (OFCGs) in the few GHz repetition frequency rates, with highly correlated modes and continuously tunable distance between them, in a compact and energy and cost efficient system that can find application in ultrafast laser dynamics studies and or in polarization-division multiplexing optical communications. The authors would like to thank VERTILAS for providing the VCSELs.

Carbon monoxide (CO) is a prominent and toxic gas mainly generated by imperfect burning in fires or ovens. For trace gas monitoring and fire detection a compact, long term stable and calibration-free CO sensor is desirable. One very interesting measuring method is Tuneable Diode Laser Absorption Spectroscopy (TDLAS), which utilizes the unique properties of Vertical-Cavity Surface-Emitting Lasers (VCSELs). Two approaches to reach the required wavelength range for the absorption lines of CO at around 2350 nm are discussed in this paper. The first approach is an expansion of the emission wavelength range of the now well-established lasers based on InP and a second and new one is fabricating VCSELs based on GaSb. From the epitaxial point of view the gain of the active material and the realization of a tunnel junction as well as optical, thermal and electrical characteristics of the mirror materials are important issues. For a proper choice of the device design the structuring of the used materials also plays a fundamental role— in particular the substrate removal. With simultaneous considerations of all these crucial issues, devices on InP and GaSb substrates have been fabricated. Both types work in continuous-wave mode, generating light in single-mode emission at the desired wavelength of the CO absorption line, which enables CO measurements down to a concentration limit of 2 ppm.

Vertical-cavity surface-emitting lasers are attractive light sources particularly for gas-sensing applications. Using the AlGaInAs/InP material system, an emission wavelength ranges from 1.3 to 2.05 μm has already been achieved [G. Boehm, M. Ortsiefer R. Shau, J. Rosskopf, C. Lauer, M. Maute, F. Kohler, F. Mederer, R. Meyer, M.-C. Amann, in: Proceedings of MBE XII, J. Crystal Growth (2002) pp. 748–753]. Within this range, absorption lines of gases like H 2 S (1590 nm), CH 4 (1654 nm), H 2 O (1877 nm) and CO 2 (2004 nm) are detectable [G. Totschnig, M. Lackner, R. Shau, M. Ortsiefer, J. Rosskopf, M.-C. Amann, F. Winter, Meas. Sci. Technol. 14 (2003) 472]. The aim of this work is a further expansion of the emission wavelength up to 2.3 μm, exploiting the well-known InP-based material system and the fabrication technique of buried tunnel junction (BTJ) VCSELs [R. Shau, M. Ortsiefer, J. Rosskopf, G. Boehm, C. Lauer, M. Maute, M.-C. Amann, in: Proceedings of SPIE, 5364 (2004) 1–15] to reach the technologically important absorption lines of carbon monoxide (CO) around 2.33 μm.

We report ultra-wide tuning of a 1550 nm BCB based high-speed MEMS-VCSEL. The MEMS is electrothermally actuated for a continuous tuning of 101 nm. Maximum output power and minimum threshold current is 3.2 mW and 2.6 mA, respectively.

The performance of two equalization techniques is experimentally compared using a 1530-nm VCSEL, 56Gb/s/A PAM-4, and direct detection over 2 km links for datacenter interconnect applications. Results on the performance evaluation in terms of DSP implementation and complexity are presented.

Silicon photonics enables optical interconnects with high bandwidth, long reach, low power consumption and scalability to very large systems with low-cost. We show that this is also possible with low-loss micron-scale silicon waveguides. We also present results from interposer chip fabricated on 12 µm SOI that enables simultaneous low loss coupling between SM fibres, micron-scale SOI chips, VCSELs, and detectors. Passive optical circuits within the interposer for wavelength multiplexing and power coupling reduce the need for external optical circuits. The interposer acts as a mechanical submount for the optoelectronics and the drivers, which results in a compact subassembly that can be easily integrated into optical modules.

We present a vision for transceiver integration on a 3 µm SOI waveguide platform for systems scalable to Pb/s. We also present experimental results from the first building blocks developed in the EU-funded RAPIDO project. At 1.3 µm wavelength 80 Gb/s per wavelength is to be achieved using hybrid integration of III-V optoelectronics on SOI. Goals include athermal operation, low-loss I/O coupling, advanced modulation formats and packet switching. An example of the design results is an interposer chip that consists of 12 µm thick SOI waveguides locally tapered down to 3 µm to provide low-loss coupling between an optical single-mode fiber array and the 3 µm SOI chip. First example of experimental results is a 4x4 cyclic AWGs with 5 nm channel spacing, 0.4 dB/facet fiber coupling loss, 3.5 dB center-tocenter loss, and -23 dB adjacent channel crosstalk in 3.5x1.5 mm2 footprint. The second example result is a new VCSEL design that was demonstrated to have up to 40 Gb/s operation at 1.55 µm.

We demonstrate the transmission of 28 Gb/s NRZ-OOK over DCF-free links up to 10 km using a monolithic VCSEL, direct detection and an MLSE-based receiver for low-cost, short-reach interconnects. DSP complexity is also investigated in terms of performance optimization.

In this paper we present an overview of the properties and applications of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) based on the InGaAlAs–InP material system. With respect to significant temperature sensitivity of active material gain as well as insufficient thermal conductivity of InP-based epitaxial compound layers, the effective thermal heat management appears as a major issue for application suitable device performance. In this context, the incorporation of a buried tunnel junction (BTJ) in connection with improved heat sinking resembles a breakthrough for long-wavelength VCSELs. With the utilization of n-type spreading layers and consequently ultralow series resistances, BTJ-VCSELs exhibit sharply reduced excess heat generation. Furthermore, the BTJ-approach enables self-aligned optical and current confinement. A hybrid dielectric stack with Au-coating yields an improved thermal heatsinking. The current status of BTJ-VCSELs encompasses a number of superior performance values. At 1.55 µm wavelength, this includes room temperature single- and multimode continuous wave (cw) output powers of more than 3 mW and 10 mW, respectively, laser operation for heat sink temperatures well exceeding 100 °C, and optical data transmission rates up to 10 Gbit/s. The versatility of compound layer composition enables arbitrary emission wavelengths within a broad range of 1.3 and 2 µm. With respect to sensing applications, BTJ-VCSELs appear as ideal components for optical detection of infrared active gases. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we present a device concept for long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the InGaAlAs/InP material system incorporating a buried tunnel junction (BTJ). A major issue of long-wavelength VCSELs is the dissipation of heat because of the low thermal conductivity of ternary and quaternary alloys. With the BTJ-VCSEL, a significant reduction of the thermal resistance is achieved by the use of a hybrid backside mirror made of a stack of amorphous dielectrics with Au-coating and the monolithic integration of a heat sink. These provide improved heat sinking capability compared to a conventional epitaxial semiconductor DBR. In addition, the tunnel junction facilitates a substitution of most of the p-doped layers by n-doped material, reducing heat generation due to ohmic losses. These features significantly improve the VCSEL characteristics. At 1.55 μm wavelength, we demonstrated single-mode cw-output powers of 1.7mW at room temperature [1], multi-mode cw-output powers of 7mW [2], laser operation up to heat sink temperatures of 110 °C [2], and optical data transmission with 10 Gbit/s and low bit error rates [3]. These are record values to the best knowledge of the authors. Using strained quantum wells, the emission wavelength can be tailored to any value in the range between 1.3 μm and 2.0 μm [4], sample results are presented for the telecommunication wavelengths 1.3 μm and 1.55 μm, 1.8 μm, and the currently upper limit of 2.0 μm. The slight wavelength tuning with driving current is brought about by the tiny volume of the devices and makes VCSELs ideal components for tunable diode laser absorption spectroscopy (TDLAS) [5, 6]. The maximum detuning typically reaches 4 nm (≙500 GHz). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Oberflächenemittierende Diodenlaser (engl. VCSEL, Vertical-cavity surface-emitting laser) werden zur raschen direkten In-situ-Molekülspektroskopie eingesetzt. Nach dem Verfahren der Absorptionsspektroskopie mittels durchstimmbarer Diodenlaser wird Sauerstoff bei 760 nm, Ammoniak bei 1540 nm, Methan bei 1680 nm sowie Chlorwasserstoff und Wasser bei 1810 nm detektiert. Druckverbreiterte und hochaufgelöste Spektren werden gezeigt und das Prinzip eines langzeitstabilen Spektrometers vorgestellt. Die Wellenlängenmodulation der VCSEL mit der Temperatur und dem Strom wird untersucht. Während der Temperaturkoeffizient in etwa derselbe ist wie für herkömmliche Diodenlaser im nahen Infrarot (DFB-Laser), lassen sich VCSEL deutlich weiter mit dem Strom durchstimmen. Darüber hinaus können VCSEL thermisch wesentlich schneller moduliert werden als konventionelle Kantenemitter. Repetitionsraten bis 5 MHz werden demonstriert. Die neu eröffneten Anwendungsfelder im Hinblick auf den weiten, modensprungfreien Durchstimmbereich (Messung bei hohem Druck, mehrere Spezies, Temperaturverteilungen) und die rasche Modulierbarkeit (Messung extrem transienter Prozesse) werden diskutiert. Weiter werden spektroskopisch interessante Eigentümlichkeiten der VCSEL (geringer Schwellstrom und Strombedarf als Vorteil für batteriebetriebene mobile Geräte, Austestmöglichkeit auf der Waferebene) beleuchtet. Die langwelligen VCSEL mit λ > 1 μm auf InP-Basis existieren noch nicht lange. Es wird angenommen, dass diese demnächst verstärkten Einzug in die Molekülspektroskopie halten werden und das Einsatzgebiet von auf Diodenlasern basierenden Geräten beträchtlich nach höheren Drücken und schwierigen Bedingungen hin erweitern werden.

A single-frequency VCSEL has been used for the first time for high-resolution spectroscopy near 1.5 μm. The incorporated buried-tunnel-junction technology enabled the realization of a long-wavelength InGaAlAs/InP VCSEL with low threshold current (0.925 mA), high output powers (0.576 mW) and low series resistance (60 Ω). The high-speed tuning capability of the long-wavelength VCSEL was investigated and used to conduct high-speed absorption spectroscopy. The peak tuning speed was measured to be 3.4 cm-1/μs and a 4.5-cm-1-wide NH3 spectrum was recorded in 2 μs. The VCSEL was used to measure highly resolved low-pressure spectra for pressures ranging from 9.6 mbar to 1 bar. The measured Doppler-broadened linewidth of 0.02 cm-1 agrees within 3% with the theoretical calculations. The availability and various advantages of 1.3–2-μm single-frequency VCSELs as compared to edge-emitting diode lasers, such as a large current tuning range even at very high tuning frequencies, and low production costs, should significantly expand the application fields for near-infrared laser gas sensors.

Buried tunnel junction vertical-cavity surface-emitting lasers (BTJ-VCSELs) are demonstrated as light sources in the wavelength range from 1.3 to 2.0 μm. Continuous-wave operation at room temperature could be achieved for the whole wavelength range. This emphasizes not only the sophisticated device design but also the excellent suitability of the material system AlGaInAs/InP. Advantages and restrictions are discussed in this paper. Transmission experiments with single-mode VCSELs at 1.55 μm show error-free data transmission at modulation frequencies up to 10 Gbit/s. At 1.68 and 1.80 μm, gas sensing experiments detecting methane and water, respectively, could be successfully performed.

A 1.8 µm wavelength single frequency InGaAlAs–InP vertical-cavity surface-emitting laser (VCSEL) was used successfully for the first time for high resolution absorption spectroscopic measurements. As a demonstration of the multi-species measurement capability, spectra of HCl, CH4 and H2O gases were measured at pressures ranging from 0.07 to 1.5 bar and compared with calculations based on the HITRAN2000 database. In general, good agreement was observed. The laser threshold was 0.9 mA, the temperature tuning rate was 0.125 nm K−1 (0.38 cm−1 K−1) and the current tuning rate was 0.9 nm mA−1 (2.75 cm−1 mA−1). A continuous mode-hop-free single frequency current tuning range of 8.4 cm−1 (2.8 nm) was achieved using a 0–4.1 mA driving current. Single frequency VCSELs show a variety of advantages compared to edge emitting semiconductor lasers, such as wide current tuning range, very high tuning speeds (MHz) and therefore very good time resolution, little susceptibility to optical feedback and low manufacturing costs. The availability of long wavelength single frequency VCSELs (1.3–2 µm) should make VCSEL the preferred choice for diode-laser gas sensing and process control applications and help to significantly expand the application fields for infrared diode-laser gas sensors.

An electrically pumped InP-based vertical-cavity surface-emitting laser (VCSEL) emitting at 1.685 µm (5935 cm−1) was used to probe rovibrational transitions of methane in the 2ν3 band at pressures ranging from 10 mbar to 1.3 bar. For the first time a long-wavelength VCSEL at 1.68 µm was used for the demonstration of high-speed gas sensing at repetition rates as high as 5 MHz. The observed tuning rate at 1 MHz was 5.2 cm−1 µs−1. The maximum continuous current tuning range was more than 16 cm−1 (4.5 nm), which is very useful for measurements in high-pressure environments. At 1 MHz the tuning range was as large as 2.6 cm−1, at 5 MHz it was still approximately 0.36 cm−1. The measured tuning rates of the VCSEL were −3.05 cm−1 mA−1 (+0.86 nm mA−1) and −0.40 cm−1 K−1 (+0.11 nm K−1). Survey spectra measured with the VCSEL were compared to calculations using the HITRAN2000 spectroscopic database and found to be in good agreement. A VCSEL was directly contacted on a section of its wafer to demonstrate 'on-chip' testing ability as opposed to edge-emitting lasers that have to be singularized and individually mounted prior to characterization for spectroscopic applications. It is expected that VCSELs will considerably expand the range of operation for diode lasers in rapid in situ species concentration measurements because of their ability of fast and far mode-hop free single longitudinal and transverse mode tuning properties.

In this letter, we explore the performance of an optical frequency comb generator (OFCG) sources based on vertical-cavity surface-emitting laser diodes. The direct gain switching (GS) technique, the indirect electro-optical (EO) technique, and a combination of both have been experimentally evaluated. We have observed that this later combination gives birth to an enhanced OFCG that offers a tunable improved comb in terms of frequency span, flatness, and coherence with respect to the sole EO approach, as it partly inherits the high-efficiency qualities of the GS-OFCG while offering a wider span.

A novel coupling approach for single mode VCSELs and planar optical waveguides is presented. The coupling is based on the embedding of the VCSELs inside the substrate and the adaptive fabrication of waveguides on top.

We present recent progress of long-wavelength VCSELs for optical communications with modulation rates between 10 and 25 Gbps and optical output powers well beyond 1 mW at 90°C which fulfill the requirements for high-performance, cost effective and green photonics.

The thermal resistance of InGaAlAs/InP long-wavelength VCSELs with buried tunnel junctions is investigated by means of a heat flow finite element analysis. Because of the low thermal conductivity of InP based compound layers, a significant improvement is obtained for a top-down mounted structure with a hybrid dielectric-metal back mirror and an InP heat spreading layer. Experimental results for such lasers show cw operation up to 75 °C with a maximum power exceeding 2 mW at room temperature for 17 μm diameter. The temperature behavior of the threshold current indicates a substantial improvement for laser operation at values even far beyond room temperature by adjusting cavity mode and spectral gain.

Recently, we demonstrated InP-based VCSELs at 1.5 μm with record device performance, achieving low threshold currents ( 1 mW) at room temperature and under continuous wave conditions (Ortsiefer et al., Appl. Phys. Lett. 76 (2000) 2179). In this presentation, we describe the epitaxial growth methods applied for the realization of these high-performance devices. For growing suitable device structures, a very good reproducibility of device parameters, such as the center wavelength of the distributed Bragg reflector, the emission wavelength of the active region and the lasing mode, as well as the possibility to fabricate new tailored devices without great effort are required. An in-situ control technique using the standard pyrometer is a simple and efficient method to monitor growth rates and to enable an in-situ adjustment of growth parameters for the control of lattice matching and layer thicknesses. Using this technique, VCSELs in the 1.5–1.8 μm wavelength range with excellent performance have been fabricated.

We present long-wavelength InGaAlAs-InP vertical-cavity surface-emitting lasers (VCSELs) with a buried tunnel junction (BTJ) and a well-defined polarization accomplished by a semiconductor/dielectric subwavelength grating (SWG). The grating is incorporated in the inner VCSEL cavity and exhibits an effective birefringence for polarizations parallel and perpendicular to the grating grooves. Theoretical modeling leads to distinct design rules for VCSELs with grating structure that deviate from the conventional design without grating. Due to the large polarization-mode separation, lasing activity is enabled only for one polarization mode. BTJ-VCSELs with properly chosen SWG parameters show predictable and full polarization stability. In addition, the relevant device parameters such as threshold current are comparable to conventional BTJ-VCSELs.

Vertical-cavity surface-emitting lasers (VCSELs) at 1.55 mum provide high modulation bandwidth and low attenuation at a low cost. Like other directly modulated lasers, laser chirp limits the link length in standard single-mode fibers at high data rates and fiber dispersion causes bit-error-rate (BER) penalty. This can be overcome by dispersion-compensating fibers (DCFs). This letter investigates the modulation performance of monolithically grown 1.55-mum VCSELs utilizing a DCF to boost the possible link length. Data-transmission experiments are performed at 10 Gb/s and dispersion-dependent BER performance is presented for the first time for this type of laser.