Frequency Up-conversion Technique Research Articles

Exciton dynamics of GaAs-Al XGa 1−XAs quantum wells by picosecond time resolved photoluminescence spectroscopy

The dynamics of exciton formation and decay are investigated in GaAs-Al XGa 1−XAs (x<0.4) multiquantum well structures under low excitation conditions by transient photoluminescence spectroscopy. The time resolution (10 ps) is achieved by using the frequency up-conversion technique. At low temperature (T < 50 K), the luminescence is dominated by localized exciton formation and recombination processes: significant Stokes shifts from the exciton absorption line, long non-exponential rise time (ranging from 200 ps to 600 ps) and short radiative lifetime (from 200 ps to 400 ps) are observed. At higher temperature (T > 80 K), the luminescence is dominated by free exciton radiative recombination with shorter formation time and much larger exciton lifetime (from 3 ns to 6 ns). We suggest that the exciton may trap efficiently at low temperature on interface defects, the areal density of which can be evaluated in a simple manner.

Real-time measurement of picosecond optical pulses from an InGaAsP diode laser using an ultrafast streak camera with infrared frequency up-conversion

A novel method for real-time measurement of ultrashort optical pulses generated from InGaAsP diode lasers at the wavelength of 1.3 μm has been realized by means of an ultrafast streak camera incorporating a frequency up-conversion technique with a LiIO3 crystal pumped by a Q-switched neodymium: yttrium aluminum garnet (Nd:YAG) laser at 1.064 μm. The optical pulse from an InGaAsP double-channel planar buried heterostructure (DC-PBH) diode laser operated by a short pulse current of 1-ns duration was measured to have a full width at half-maximum (FWHM) of approximately 28 ps by single shot scanning with the temporal resolution of 8 ps. Using a 15-mm-long LiIO3 crystal and 500-W peak power of the pumping laser pulse focused at 400 μm in diameter, the up-conversion efficiency and minimum detectable peak power of the diode laser pulse at 1.3 μm were estimated to be approximately 0.65% and 1 mW, respectively. This technique can be widely utilized for real-time detection of ultrashort optical pulses in the wavelength range beyond 1–10 μm or more.