J. Tamil

A miniature tunable coupled-cavity laser constructed by micromachining technology

This letter presents a miniature tunable coupled-cavity laser by integrating a Fabry-Perot chip, a gain chip and a deep-etched parabolic mirror using micromachining technology. The mirror is to actively adjust the gap between chips, enabling the optimal mode selection. Single-mode operation with a tuning range of 16.55nm and a side-mode-suppression ratio of >25.1dB is demonstrated. The device overcomes phase mismatching and instability problems encountered in conventional fixed-gap coupled-cavity lasers.

A micromachined tunable coupled-cavity laser for wide tuning range and high spectral purity.

This paper presents the design and experimental study of a coupled-cavity laser based on the micromachining technology for wide tuning range and improved spectral purity. The core part of this design utilizes a deep-etched movable parabolic mirror to couple two identical Fabry-Pérot chips and thus allows the active adjustment of the cavity gap so as to optimize the mode selection and to increase the tuning range as well. In experiment, the laser achieves the single longitudinal mode output over 51.3 nm and an average side-mode-suppression ratio of 22 dB when the tuning current varies from 5.7-10.8 mA. The measured wavelength tuning speed is 1.2 micros and the single mode output is stable at any wavelength when the tuning current is varied within +/- 0.06 mA. Compared with the conventional fixed cavity gap coupled-cavity lasers, such design overcomes the phase mismatching and mode instability problems while maintaining the merit of high-speed wavelength tuning using electrical current.

Tunable dual-wavelength laser constructed by silicon micromachining

This paper presents a tunable dual-wavelength laser by integration of a semiconductor gain chip with silicon-micromachined grating and mirrors onto a silicon substrate. The wavelength tuning is demonstrated by rotating the micromirror. With one wavelength being tuned and the other fixed, the laser output presents a tunable spectral separation from −28.38to+24.18nm. The laser output reaches 2.9mW with far-field divergences of 37° and 30° in the vertical and horizontal directions, respectively. Besides, line broadening is observed with the reduction of the spectral separation.

A MEMS digital mirror for tunable laser wavelength selection

This paper presents a digital mirror for tunable laser wavelength selection using microelectromechanical systems (MEMS) technology. The digital mirror which has discrete reflection spectrum is totally different compared to the current broadband mirrors MEMS tunable lasers [1–3]. The reflection of the digital mirror can be tuned by digital pumping signals which promise fast output wavelength switching. The experimental results show that the output wavelength of the MEMS tunable laser using the digital mirror has high tuning resolution without increasing the physical length of the internal cavity of the tunable laser. The output wavelength of tuning resolution can reach 0.2 nm and the bandwidth is around 0.04 nm.

MEMS Optical Logic NOR Gate using Integrated Tunable Lasers

This paper presents an optical logic NOR gate constructed by two MEMS tunable lasers and a Fabry-Pérot (FP) laser chip. The key idea is that the FP chip is directly controlled by two tunable optical signals via the physical mechanism of injection locking. Compared with other fiber-based gating mechanisms, this logic operation only depends on the optical power without need for accurate phase matching or polarization control. In experiment, the logic NOR function is demonstrated successfully at 100 Mb/s with an extinction ratio of more than 20 dB, and it has a potential to reach higher speed of 10 Gb/s level. The work demonstrates a MEMS single-chip solution for optical logic gates with the advantages of compact footprint, simple optical alignment and easy integration, and may find potential applications in high-speed all-optical communication networks.

A Micromachined Thermo-Optic Tunable Laser

The paper presents a thermo-optic tunable laser that makes use of a micromachined etalon to form the external cavity. The wavelength tuning is obtained by the thermo-optic effect of the silicon material. In experiment, a wavelength tuning range of 14 nm is demonstrated by applying a heating current of 18.7 mA to a deep-etched silicon etalon of 206 ¿m wide. In the dynamic test, this laser measures a tuning speed of 3.2 ¿s, which is much faster than the typical speed of 1 ms as given by the previous MEMS tunable lasers that rely on the motion of mirrors or gratings. Since this laser is based on a different tuning mechanism of thermo-optic effect and requires no mechanical movement, it possesses many advantages such as fast speed, simple configuration and planar structure, and will broaden the applications of MEMS tunable lasers.

MEMS Laser with Tunable Wavelength and Polarization using Optical Tunneling Effect

This paper presents a micromachined tunable laser that utilizes a silicon optical tunneling structure to tune both the polarization state and the wavelength of the laser output. The device is fabricated on silicon-on-insulator wafer using deep reactive ion etching. In experiment, the wavelength and the polarization are tuned by heating up the silicon optical tunneling structure via the thermo-optic effect. A 90° change of polarization direction is obtained using a heating current of 61.2 mA, and a wavelength tuning of 2 nm is also demonstrated. The output spectrum shows a high suppress ratio above 30 dB. Compared with the previous MEMS tunable lasers that have a random or fixed polarization state, this device provides a special capability in tuning the polarization state in addition to the wavelength, and would find niche applications in biomedical research, interferometry, coherent communications, instrumentations and sensors.

Real Pivot Mechanism of Rotary Comb-Drive Actuators for MEMS Continuously Tunable Lasers

This paper presented the theoretical and experimental studies on a new mechanism of real pivot by use of a double-clamped beam. Comparison with the conventional virtual pivot formed by a cantilever beam, such real pivot provides large rotation angle and small position shift, which is key for the MEMS tunable lasers to obtain continuous wavelength tuning over a wide range. In experiment, the real pivot is able to produce a rotation angle of 4.7 degrees regardless of a depth variation of 16 % over the double-clamped beam due to fabrication error. In contrast, the virtual pivot has only 2.4 degrees in the presence of 4 % depth reduction. The real pivot design is more suitable for the MEMS tunable lasers as it is simple, symmetric, robust and allowable for single-chip integration.

A Review of Different Types of Photonic MEMS Tunable Lasers

In this paper, four different types of miniaturized Microelectromechanical Systems (MEMS) based tunable lasers, from photonic MEMS laser designs to fabrication techniques, are introduced. These tunable lasers are MEMS external cavity laser, injection-locked laser, coupled-cavity laser, and dual-wavelength laser. The properties, functionalities and performances of the MEMS-based tunable lasers are individually discussed based on their experimental results. The potential applications in fiber optical communications are also identified. These tunable lasers, which are more innovative in terms of design, specifications and configurations compared to traditional lasers, also provide significant improvements in their functionalities.

Characteristics of micromachined injection locking lasers

This paper reports a theoretical and experimental study of a MEMS injection-locked laser (ILL). The micromachined injection-locked laser consists of a MEMS tunable laser (master) and a Fabry-Pérot multimode laser (slave) that is integrated by using deep RIE processes onto a single chip. Based on the experimental results, hysteresis property in asymmetrical tuning curve is observed and optical bistability is found. Superior performances in terms of stability and narrow linewidth have been achieved.