The cause of the laser failure was overheating due to accumulated dusts on the air-filter of the power supply unit. I have to make sure that the filter is vacuum-cleaned every 6 months. Laser is originally purchased in 2005. The service contract (12k per year) would have covered the replacement cost, but we were not on the service contract, so we did repair it at 11k. The laser wont break down every year, so it is still economical. By paying 12k every year for 12 years, we could buy a new laser.