InP Quantum Dot Lasers

The aim is to develop short wavelength quantum dot lasers (640-780nm) for operation at the technologically important wavelengths in the red part of the spectrum.

This makes use of InP quantum dots grown on AlGaInP and ultimately on GaAs substrates. A complementary aim is to gain further insight into the physics of low-dimensional solids as applied to semiconductor lasers.

Interest is driven by the potential for low threshold current density (Jth), reduced temperature sensitivity of Jth and reduced sensitivity to processing induced damage while operating in a wavelength range appropriate for sensing, medical and biophotonic applications.

Activities

Some of our specific achievements to date include:

• The development of low threshold current density (150Acm-2 at 300K for 2mm long lasers with uncoated facets), which is only a factor of 2 poorer than the best, longer established, InAs lasers with the same optical loss, and over a wide wavelength range.
• Use of Ga composition of dot capping layer alone to adjust the emission wavelength of the quantum dot states (696-750nm).
• Understanding of the physics of the temperature dependence of threshold current in these structures, followed by demonstration of significant improvement in the temperature dependence and operation up to 400K.
• Measured absorber / gain dynamics prove that the gain exhibits an ultrafast recovery within 200 fs, which is even faster than state-of-the-art InAs/GaAs quantum-dot amplifiers and is promising for optical signal processing at high bit rates.
• Measured alpha factor similar to InGaAs dots.

Findings

Further advances are required in:

• Understanding and developing temperature insensitive operating wavelength.
• Development of DBR lasers producing multi-wavelength output from the same gain medium.
• Development of monolithically integrated lasers, detectors and fluid channel for lab-on-a-chip application.

Publications

• Elliott, S. et al. 2012. Catastrophic optical bulk damage in InP 7xx emitting quantum dot diode lasers. Semiconductor Science and Technology 27 (10) 102001. (10.1088/0268-1242/27/10/102001)
• Elliott, S. et al. 2012. The effect of strained confinement layers in InP self-assembled quantum dot material. Semiconductor Science and Technology 27 (9) 94008. (10.1088/0268-1242/27/9/094008)
• Al-Ghamdi, M. et al., 2011. Dot density effect by quantity of deposited material in InP/AlGaInP structures. IEEE Photonics Technology Letters 23 (16), pp.1169-1171. (10.1109/LPT.2011.2157910)
• Shutts, S. et al. 2011. Deep etched distributed Bragg reflector (DBR) InP/AlGaInP quantum dot lasers. Presented at: Novel In-Plane Semiconductor Lasers X San Francisco, CA, USA 25-28 January 2011. Published in: Belyanin, A. and Smowton, P. M. eds. Proceedings of Novel In-Plane Semiconductor Lasers X, San Francisco, USA, 25-28 January 2011. Vol. 7953.SPIE Proceedings Vol. 7953. Bellingham, WA: IEEE. , pp.795308. (10.1117/12.876454)
• Smowton, P. M. et al. 2011. Temperature-dependent threshold current in InP Quantum-Dot Lasers. IEEE Journal of Selected Topics in Quantum Electronics 17 (5), pp.1343-1348. (10.1109/JSTQE.2011.2115235)
• Langbein, W. W. et al. 2010. Ultrafast gain dynamics in InP quantum-dot optical amplifiers. Applied Physics Letters 97 (21) 211103. (10.1063/1.3518715)
• Smowton, P. M. et al. 2010. Effect of growth temperature on InP QD lasers. IEEE Photonics Technology Letters 22 (2), pp.88-90. (10.1109/LPT.2009.2036245)

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The project team

Project lead

Team

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  Professor Peter Blood

  Honorary Distinguished Professor

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  Professor Wolfgang Langbein

  Head of Condensed Matter and Photonics Group