Light amplifiers are very important devices for optical fiber communication and all-optical signal processing. Waveguide-type laser amplifiers are proposed to be constructed in 1 at.% Nd doped Yittrium Gallium Garnet crystalline thin films deposited on Yittrium Aluminium Garnet substrates. The amplifiers are classified into a traveling wave (TW)type and a Fabry-Perot(FP)cavity-type. Numerical calculations of gains, SN ratios and pulse response of the optical signal for both amplifiers are carried out using the rate equations for a four-level system of Nd ions in the garnet thin-film with a thickness of about 2.5 µm. For the TW-type amplifier, the net gain and SN ratio are about 10 dB and 20 dB at the signal power of 10-6 W and the pumping power of 210-4W. For the FP-type amplifier, the net gain at the signal power of 10-7W and the pumping power of 10-4W is twice that for the TW-type amplifier. The net gain and SN ratio are 6 dB and 8 dB. Numerical calculations of the pulse response of the optical signals are carried out. The rise and fall times of the output pulse for the TW- and FP-type amplifiers are about 0.01 ns and 1 ns, respectively.