  Single crystals of thallium-based cuprates with the general formula
Tl$_{2}$Ba$_{2}$Ca$_{n-1}$Cu$_{n}$O$_{x}$(n=1,2,3) have been grown by the flux
method. The superconducting transition temperatures determined by the ac
magnetic susceptibility are 92 K, 109 K, and 119 K for n=1,2,3 respectively.
X-ray diffraction measurements and EDX compositional analysis were described.
We measured in-plane optical reflectance from room temperature down to 10 K,
placing emphasis on Tl-2223. The reflectance roughly has a linear-frequency
dependence above superconducting transition temperature, but displays a
pronounced knee structure together with a dip-like feature at higher frequency
below T$_c$. Correspondingly, the ratio of the reflectances below and above
T$_{c}$ displays a maximum and a minimum near those feature frequencies. In
particular, those features in Tl2223 appear at higher energy scale than Tl2212,
and Tl2201. The optical data are analyzed in terms of spectral function. We
discussed the physical consequences of the data in terms of both clean and
dirty limit.
