Persistent Spectral Hole-Burning of CuCI Semiconductor Quantum dots

Yasuaki Masumoto, Koji Sonobe, Naru Sakakura

R. Heitz, Till Warming, Florian Guffarth +4 more

Yasuaki Masumoto

The persistent spectral hole-burning (PSHB) phenomenon was observed in semiconductor quantum dots, CdSe , CuCl , and CuBr , embedded in glass and crystal. In inhomogeneously broadened exciton absorption spectra of these dots, the narrow bleaching hole and its associated structure are made by the narrowband laser excitation and are conserved for more than several hours at 2 K after the laser irradiation. The observation of the PSHB phenomenon in these four kinds of samples shows the generality of the phenomenon in semiconductor quantum dots and requires the existence of more than one ground-state configurations of the total system consisting of quantum dots and surrounding matrix. It means that not only the size distribution but also these ground-state configurations give inhomoge-neous broadening to semiconductor quantum dots. Thermally annealing and light-induced hole-filling phenomena were observed. Hole-burning and hole-filling mechanisms are discussed. Quantum dots consisting of 103–104 atoms behave like molecules or ions in matrix to give the PSHB phenomenon.

Yasuaki Masumoto

Persistent spectral-hole-burning (PSHB) phenomena have been observed in many kinds of semiconductor quantum dots (QDs). Luminescence hole burning and charged excitons have been observed in CuCl QDs in NaCl crystals. The observed PSHB phenomena are explained by the ionization of QDs. The energy of photoionized QDs is changed from the original energy and their new energies depend on the spatial arrangement of trapped carriers. Quantum confinement of carriers and the resulting strong Coulomb interaction between confined carriers and trapped carriers cause the energy change. PSHB has been widely applied to site-selective spectroscopy of QDs. Size-dependent excited exciton quantum states in CuCl quantum cubes, size-dependent excited electron-hole quantum states in CdTe QDs and renormalization of longitudinal optical phonons confined in CuCl QDs have been revealed by studying sideband holes. This also allowed the measurement of accumulated photon echo, which clarified the very sharp homogeneous spectral linewidth of QDs under weak excitation conditions.

Joseph J. Berry, Richard P. Mirin, Kevin L. Silverman

Tadashi Kawazoe, Yasuaki Masumoto Yasuaki Masumoto

Formation efficiencies of the persistent holes in various kinds of cuprous halides quantum dots, namely CuCl, CuBr and CuI quantum dots, embedded in glass or alkali halide crystals, were measured. The highest quantum efficiency of 0.097 was obtained at 2 K for CuCl quantum dots in glass. The persistent absorption decrease of quantum dots caused by a photon is larger than that of the most efficient ionic or molecular persistent hole-burning materials by 3 orders of magnitudes. The high sensitivity shows that the persistent hole-burning phenomenon in semiconductor quantum dots has potential for application in the multiple optical memory devices.