Integrated Laser Sources
Photonic integration allows sources with electro-optic phase modulators, optical filters and many other passive components on a single chip of several square millimetres.
Extended wavelength ranges are feasible with the InP material system, opening up new applications in sensing, security, safety and metrology. A recent breakthrough with quantum dot epitaxy has opened up the longer wavelength window of 1600-1800 nm region which is highly relevant to Optical Coherence Tomography (OCT) imaging technologies. We are developing a semiconductor optical chip with a laser source that can achieve the tuning requirements for rapid spectral scanning and plan to integrate further OCT apparatus for full system-on-chip solutions. The example laser system shown below uses a quantum dot optical amplifier combined with one or two electro-optically tunable wavelength filters. These are tunable Arrayed Waveguide Gratings with electro-optic phase modulators in the arms of the AWG. Programmable electronics control the 40 to 50 phase modulators to scan the laser in any possible way.
Tunable sources are being developed with simplified electrical control to ensure predictable oscillating wavelengths. We develop a scheme in which we use a laser operating at a discrete set of equally spaced wavelengths that can be matched to the internationally standardized telecommunication wavelengths (ITU-grid). In the framework of the iPHOS FP7 EU project linear and ring dual wavelength lasers have been fabricated in the COBRA and Oclaro fabrication platforms for millimeter wave communications applications. Devices have been packaged and are being used by project partners in Germany and Spain. In the STW LWAVETECH project we focus on tunable lasers for gas detection based on an AWG laser and new interferometer lay-out structures. A library for pulse lasers is also being developed for the generic integration platform.
Narrow-linewidth and multi-wavelength lasers using our filtered feedback techniques and MMI-based integrated reflectors designed to simultaneously transmit at four different wavelengths, were shown to have good lasing characteristics. Good output power (0 dBm in fiber), good side-mode suppression (> 40 dB) and a narrow linewidth (< 140 kHz) are already demonstrated. Multi-color lasers with monolithically integrated RF modulators (> 10 GHz) have also been made and used in an analog photonic link in a photonic beam former demonstrator for a smart antenna at ASTRON. Multiwavelength sources using DBR-lasers integrated with AWGs are also demonstrated for use in advanced WDM-TDM Fibre-to-the-Home networks. Mach-Zehnder modulators integrated with these lasers could be operated up to 12.5 Gbps with output power up to 4 mW in the fiber.
Lenstra, D. (2013). Relaxation oscillation dynamics in semiconductor diode lasers with optical feedback. IEEE Photonics Technology Letters,25(6), 591-593.
Khoder, M., Verschaffelt, G., Modeste Nguimdo, R., Leijtens, X.J.M., Bolk, J. & Danckaert, J. (2013). Digitally tunable dual wavelength emission from semiconductor ring lasers with filtered optical feedback. Laser Physics Letters, 10(7)
Lawniczuk, K., Kazmierski, C., Provost, J.G., Wale, M.J., Piramidowicz, R., Szczepanski, P., Smit, M.K. & Leijtens, X.J.M. (2013). InP-based photonic multiwavelength transmitter with DBR laser array. IEEE Photonics Technology Letters, 25(4), 352-354.
Zhao, J., Lenstra, D., Lemos Alvares Dos Santos, R.M., Wale, M.J., Smit, M.K. & Leijtens, X.J.M. (2012). Feedback phase influence on an integrated filtered-feedback laser. IEEE Photonics Technology Letters, 24(23), 2195-2107.
Ermakov, I.V., Beri, S., Ashour, M., Danckaert, J., Docter, B., Bolk, J., Leijtens, X.J.M. & Verschaffelt, G. (2012). Semiconductor ring laser with on-chip filtered optical feedback for discrete wavelength tuning. IEEE Journal of Quantum Electronics, 48(2), 129-136.
Zhao, J., Lenstra, D., Lemos Alvares Dos Santos, R.M., Wale, M.J., Smit, M.K. & Leijtens, X.J.M. (2012). Stability of a monolithic integrated filtered-feedback laser. Optics Express, 20(26), B270-B278.
Tilma, B.W., Jiao, Y., Kotani, J., Smalbrugge, E., Ambrosius, H.P.M.M., Thijs, P.J.A., Leijtens, X.J.M., Nötzel, R., Smit, M.K. & Bente, E.A.J.M. (2012).Integrated tunable quantum-dot laser for optical coherence tomography in the 1.7 μm wavelength region. IEEE Journal of Quantum Electronics,48(2), 87-98.
Nguimdo, R.M., Verschaffelt, G., Danckaert, J., Leijtens, X.J.M., Bolk, J. & Sande, G. van der (2012). Fast random bits generation based on a single chaotic semiconductor ring laser. Optics Express, 20(27), 28603-28613.
Jiao, Y., Veldhoven, P.J. van, Smalbrugge, E., Smit, M.K., He, S. & Bente, E.A.J.M. (2012). Measurement and analysis of temperature-dependent optical modal gain in single-layer InAs/InP(100) quantum-dot amplifiers in the 1.6- to 1.8-µm wavelength range. IEEE Photonics Journal, 4(6), 2292-2306.
Tilma, B.W., Jiao, Y., Veldhoven, P.J. van, Smalbrugge, E., Ambrosius, H.P.M.M., Thijs, P.J.A., Leijtens, X.J.M., Nötzel, R., Smit, M.K. & Bente, E.A.J.M. (2011). InP-based monolithically integrated tunable wavelength filters in the 1.6–1.8 μm wavelength region for tunable laser purposes.Journal of Lightwave Technology, 29(18), 2818-2830.
Docter, B., Pozo, J., Beri, S., Ermakov, I.V., Danckaert, J., Smit, M.K. & Karouta, F. (2010). Discretely tunable laser based on filtered feedback for telecommunication applications. IEEE Journal of Selected Topics in Quantum Electronics, 16(5), 1405-1412.