Electrical detection of photoinduced spins both at room temperature and in remanence

Abstract

We demonstrate a photodetector with ferromagnetic contacts which can electrically detect the polarization degree of incoming light using spin filtering of photoinduced spin-polarized electron currents. Our structure is a pin diode with a single GaAs quantum well as active region and a Fe∕Tb multilayer on top of a MgO tunnel barrier as n-contact where the spin-polarized electron current is filtered. The photocurrent depends on the magnetization of the contacts and on the polarization of the injected light. We prove that even in remanence and at room temperature the degree of circular polarization of the incident light can be unambiguously determined by the photocurrent intensity.

Birefringence controlled room-temperature picosecond spin dynamics close to the threshold of vertical-cavity surface-emitting laser devices

“…This time-resolved analysis shows that our experimental procedure controls the polarization of the VCSEL output by the spin-polarized excitation as concluded earlier from time-integrated measurements. 16 The frequency of oscillations does not depend on excitation conditions within the experimental accuracy. Accordingly, emission of only one circular polarization as it may be desired for applications cannot be easily achieved with the control parameters available in the present setup ͑see below͒.…”

“…In a recent letter, we studied the time-integrated polarization degree of commercial electrically pumped VCSELs and showed that even dominantly electrically pumped devices can show spin dynamics with additional spin-polarized optical excitation. 16 In this letter we present a time-resolved analysis of the complex polarization dynamics of spinpolarized VCSELs close to threshold and discuss ultrafast modulation scenarios in future spin-VCSELs. 17,18 Since no electrically pumped room-temperature spin-VCSEL device is available yet, we chose a hybrid excitation scheme.…”

“…1 and further details can be found in Ref. 16. All experiments were performed at roomtemperature and without any external magnetic fields.…”

“…The modelocked Ti:sapphire laser emits laser pulses at 770 nm with a pulse width of 80 fs and a repetition rate of 75.5 MHz. After propagating through a single mode fiber, installed for reasons of flexibility and beam shaping, 16 the laser pulses are broadened to approximately 3 ps. The polarization state of the excitation can be controlled by using a pair of retardation plates.…”

Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

“…A comprehensive understanding of the interplay between the spin excited emission and cavity anisotropies as birefringence and dichroism of the devices is necessary in order to develop efficient spin-VCSELs 11,12 . Upon cw excitation we have demonstrated that the linear polarization predetermination can be suppressed with spin polarized injection 13,14 . For the practical application, the temporal spin dynamics is of primary interest, so a comprehensive understanding of the complex interplay of spin dynamics, carrier density, photon density and devices parameters is highly desirable.…”