For a secure data transmission while using quantum cryptography, the emission of single photons is essential. Emitting more than one photon at a time leads to photon number splitting (PNS), which allows eavesdropping.
One approach to avoid this problem is to use a vertical-cavity surface-emitting laser (VCSEL) to excite quantum dots (QD) which only emit single photons. This technique allows the tuning of VCSEL cavities by external stress using piezoelectric actuators.
The lateral and the vertical expansion of the actuator controls the cavity modes and QD emission wavelengths. This allows the resonant tuning of the VCSEL with the QD excitons. The yield of single photons is also increased by using higher operating frequencies and by a significant reduction of empty pulses.
Highly increased yield of single photons
High Purcell and quality factors
Compensation of temperature fluctuation
Not known
The invention is applicable for quantum cryptography and for data transmission as used in the communication industry.
Ina Krueger
