We report the design and manufacturing of a tunable VCSEL with an HCG MEMS mirror and an integrated detector oblique to the optical cavity for measuring output power without disturbing the laser cavity. This allows for a single laser device with integrated power monitoring capabilities that can be used in concert with external electronics to stabilize the power or monitor optical feedback of the device for sensing applications. The HCG tunable VCSEL is modified to incorporate a sacrificial layer capable of detecting light at the VCSEL’s operating wavelength. For the MEMS release process, the sacrificial layer is removed from the optical cavity defined by the VCSEL mirrors and active region. The release process is designed to create a cavern around the optical cavity and walls of such cavern are composed by sacrificial layer material. Thus, the sacrificial layer material is removed from the optical cavity, but is kept surrounding it. Light scattered at the interface semiconductor-air hits the cavern walls and modifies current through the MEMS terminals (Idet). Any change in VCSEL output power (Pout) is directly related to a change on Idet through MEMS terminal, creating a direct relationship of Pout vs. Idet. To the best of our knowledge, there is no previous report of a VCSEL with integrated oblique intracavity detector.

Polarization-sensitive optical coherence tomography (PS-OCT) is a non-destructive and three-dimensional imaging technique that can provide polarization properties, e.g., phase retardation and the optical axis, as well as architectural information similar to conventional OCT from the sample. In this study, we have developed a high-speed PS-OCT imaging engine by using a novel wavelength-swept laser light source based on a high-contrast grating vertical-cavity surface-emitting laser (HCG-VCSEL). Example PS-OCT imaging including the human fingernail junction, 3D plastic printing material, and the chicken breast tissue demonstrated the depth-resolved measurement of the multifunctional information of the sample with PS-OCT and HCG-VCSEL light source at an A-scan rate of 250 kHz.

We present a high-speed swept-source optical coherence tomography (SS-OCT) imaging system using an electrically pumped, micro-electromechanical-system (MEMS) tunable HCG-VCSEL operating at the 1060 nm wavelength regime. Comparing to existing MEMS VCSEL light sources for SS-OCT, a movable high-contrast grating (HCG) is used as the top mirror of the laser cavity, replacing the conventional distributed Bragg reflector mirror design. By applying a reverse bias voltage, the HCG mirror actuates downward toward the VCSEL cavity, changing the effective cavity length and resulting in wavelength tuning responses. The developed SS-OCT system allows an A-scan rate of 250 kHz, a detection sensitivity of 98 dB, and an axial imaging resolution of 22 µm (full-width at half-maximum (FWHM), in air). The A-scan rate can be further improved to 500 kHz if both the backward (long to short wavelength) and forward laser sweep are used. In the experimental setup, a dual-channel acquisition scheme was utilized to provide calibration of the OCT signal with a separate calibration interferometer. Volumetric imaging of the human fingernail/nail fold junction in vivo shows the feasibility of providing high-speed imaging of the tissue architectures. The MEMS tunable HCG-VCSEL light source can provide high-speed OCT imaging with a more compact light source footprint and potentially a lower cost

We report recent advances in electrically-pumped 1050 nm and 1550 nm micro-electro-mechanically-tunable verticalcavity surface emitting-lasers (MEMS-VCSELs). We demonstrate a single-mode, continuous, mechanical tuning range of 73 nm with high output power and low threshold current performance for the 1050 nm devices. To the best of our knowledge, 73 nm is a record tuning value for an electrically-pumped tunable VCSEL with a tuning speed >250 kHz, making them highly desirable for next generation OCT and other swept source applications. 10 Gbps 1550-nm DWDM tunable SFP+ modules based on an HCG-VCSEL are demonstrated with an embedded communications channel for automatic wavelength tuning and locking for low cost FTTx and front haul network applications.

We demonstrate interferometrically that a laser with a mechanically compliant output coupler can optically self-cool its fundamental mechanical mode from room temperature to an effective temperature of 30 K.

We report an electrically-pumped 1050 nm micro-electro-mechanically-tunable vertical-cavity surface-emitting-laser (MEMS-VCSEL) with a record single-mode, continuous, mechanical tuning range of 73.2 nm with high output power and low threshold current performance, which is suitable for next generation swept-source optical coherence tomography (OCT) imaging and sensing applications.

We report a high-contrast metastructure (HCM) mirror as a novel beam-shaping element for vertical-cavity surface-emitting lasers (VCSELs). The metastructure is monolithically integrated as a part of the VCSEL, working both as a micro-electromechanical tunable mirror and output beam shaper. While providing broadband, high reflection to support lasing of the VCSEL, its angular transmission characteristics can be tailored to shape the angular profile of the output beam. Various far-field emission patterns are demonstrated for single-mode, 1550 nm VCSELs with different HCM designs. We further demonstrated two-faced VCSELs with different mode profiles from their two mirrors, for the first time, to the best of our knowledge. This bifunctional integrated metastructure opens new avenues to engineer a VCSEL's emission properties, and shows great promise for applications that desire highly compact emitters integrated on a chip to provide versatile functionalities. (c) 2018 Optical Society of America

1550-nm DWDM tuneable SFP+ modules based on an HCG-VCSEL are demonstrated with an embedded communications channel for wavelength tuning and locking using a draft ITU-T G.METRO specification for low cost front haul network applications.

Various far-field emission patterns are demonstrated for single-mode 1550-nm VCSELs, incorporating high-contrast gratings as both the reflective laser mirror and transmission modulation plate. This approach opens new avenues to engineer a VCSEL’s emission properties.

We report tunable VCSELs emitting around 1060 nm, enabled by high-contrast grating (HCG) mirror. Single-mode continuous-wave (CW) operation up to 110 °C is demonstrated, with room-temperature single-mode output power >1.3 mW at a very low threshold of ~300 µA. The obtained thermal resistance of 0.88 °C/mW is low for VCSELs with an oxide-confined laser aperture. A wide, continuous tuning range up to 40 nm was achieved with electrostatic and thermal tuning, at a fast tuning speed up to 1.15 MHz. In addition, we developed transverse-mode control designs of HCGs to greatly improve the single-mode yield of oxidized VCSELs. The cost-effective, wafer-scale fabrication makes these VCSELs promising as tunable light sources for swept-source optical coherent tomography (SS-OCT) and LiDAR applications.

In this talk, we review recent progress of monolithic, wavelength-swept vertical-cavity surface-emitting lasers (VCSELs) and their applications. A typical electrically-pumped VCSEL consists of two oppositely doped distributed Bragg reflectors (DBRs) with a cavity layer in between. In the center of the cavity layer resides an active region, consisting of multiple quantum wells. Due to the short cavity length which results in a very large longitudinal mode spacing, there is only one longitudinal mode that lases. Lasing wavelength can be continuously swept with continuously varied cavity length. The first generation of sweptable tunable VCSELs were demonstrated with part or entire top DBR be held by a micro-electro-mechanical structure (MEMS) and the lasing wavelength is varied by moving the MEMS with an electric bias. Electrically-pumped, tunable VCSELs emitting at 850-nm, 940-nm, 1060-nm, 1300-nm and 1550-nm were all demonstrated. These VCSELs are demonstrated with high modulation rate and coherent lengths, well poised for optical communications applications in datacenters, fiber-to-the-home and metropolitan area networks. Recently, optically pumped tunable VCSEL has been demonstrated with an ultrawide tuning range. In addition, new applications in optical coherence tomography and LIDAR are particular interesting for continuously tunable VCSEL. Finally, replacing the movable top DBR mirror by an ultra-thin high-contrast grating (HCG), the sweep rate of the tunable VCSEL was reported to drastically increased to 1~10 MHz, which can enable many real-time 3D imaging applications. We will discuss the design criteria, characteristics, challenges, advances and prospects of wavelength-swept MEMS-VCSEs.

We demonstrate a 1550-nm broadband self-swept VCSEL with 23-nm wavelength range at 131 kHz sweep rate. The mechanical oscillation of the ultra-lightweight HCG top mirror is excited optomechanically by photons inside the lasing cavity.

Cavity optomechanics explores the interaction between optical field and mechanical motion. So far, this interaction has relied on the detuning between a passive optical resonator and an external pump laser. Here, we report a new scheme with mutual coupling between a mechanical oscillator supporting the mirror of a laser and the optical field generated by the laser itself. The optically active cavity greatly enhances the light-matter energy transfer. In this work, we use an electrically-pumped vertical-cavity surface-emitting laser (VCSEL) with an ultra-light-weight (130 pg) high-contrast-grating (HCG) mirror, whose reflectivity spectrum is designed to facilitate strong optomechanical coupling, to demonstrate optomechanically-induced regenerative oscillation of the laser optomechanical cavity. We observe >550 nm self-oscillation amplitude of the micromechanical oscillator, two to three orders of magnitude larger than typical and correspondingly a 23 nm laser wavelength sweep. In addition to its immediate applications as a high-speed wavelength-swept source, this scheme also offers a new approach for integrated on-chip sensors.

We demonstrate wavelength-tunable SFF transceivers operating at 1550 nm using a tunable VCSEL with a high contrast grating (HCG) as the output mirror. Tunable HCG VCSELs with a similar to 25 nm mechanical tuning range and over 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for next generation DWDM communications systems in access networks and data centers.

A continuously tunable, high-speed bifunctional device is demonstrated as tunable resonant cavity detector and VCSEL by simply changing bias polarity. Tunable receiver with 33.5-nm wavelength range is obtained. A VCSEL-VCSEL bidirectional communication link is demonstrated.

We demonstrate wavelength-tunable VCSELs using high contrast gratings (HCGs) as the top output mirror on VCSELs, operating at 1550 nm. Tunable HCG VCSELs with a similar to 25 nm mechanical tuning range as well as VCSELs with 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for WDM communications systems.

We report a tunable 1550-nm detector using a monolithic high-contrast grating (HCG) vertical-cavity surface-emitting laser. The detector is resonance enhanced, with a responsivity demonstrated as large as 1 A/W. It features a strong wavelength selectivity over a wide tuning range, enabled by the highly reflective microelectromechanically actutable HCG mirror. A tuning range of 33.5 nm and a spectral width of 1.2 nm are demonstrated. We show that it can select a specific data channel with 1 Gb/s data rate and reject adjacent channels 4 nm away. Higher detection speed at 10 Gb/s is also demonstrated. We show three special functionalities of this tunable detector. The first one is dual functionality-not only as a receiver but also a transmitter-with a simple change of its bias polarity. Though long sought after, a tunable bifunctional device had not been realized before. An error-free high-speed link over 25 km single-mode-fiber is demonstrated between two such devices. The second special property is its wavelength-self-tracking configuration, i.e., its resonance wavelength can automatically track the input light's wavelength. Finally, we demonstrate its use as a fast on-chip optical spectrometer, with an operation speed at 200 kHz. This tunable detector would be useful for a variety of wavelength-division-multiplexing network and lab-on-a-chip systems.

A new measurement scheme to characterize MEMS-VCSEL linewidths is demonstrated. Linewidth in the range of 40~60MHz is measured for 1550-nm high contrast grating VCSELs. We identify key contributors of the Brownian-motion-induced broadening for future optimization.