Amplified spontaneous emission(ASE) from the structure comprised of a poly(2-methoxy-5-(2′-ethylhexyloxy)-1

4-phenylene vinylene) (MEH-PPV) film deposited on SiO

2

was reported.The change of the emission spectra detected from the edge of the sample showed a clear threshold and gain narrowing phenomenon when increasing the excitation intensity.With increasing the thickness of the polymer film

the threshold of ASE diminishes and the net gain increases.A maximum net gain of 25.03 cm

-1

and a minimum threshold of 2.2 μJ/pulse are obtained at the thickness of 150 nm.Our results indicate that MEH-PPV is an attractive gain medium in optically pumped polymer lasers and amplifier.