Power extraction investigations for a 10-kW-class supersonic COIL

Abstract

In a stable resonator configuration, the output power and the power density distribution of a chemical oxygen-iodine Laser (COIL) were measured for various outcoupling geometries: Diaphragms with slit apertures of various size were introduced intracavity in front of the outcoupling mirror. The slit was placed at different positions along the flow axis. Furthermore, outcoupling mirrors ofvarious reflectivity were used.For all experimental conditions the measured power density distribution at the outcoupling mirror reveals strong symmetry effects: The beam patterns are always symmetric to the resonator axis. The beam shape and the beam size are defined by the hardware aperture that is nearest to the resonator axis. As a function ofthe slit width, the laser output power saturates well before the aperture of the resonator is fully opened. 50%ofthe maximum output power were achieved at a width of 6 mm only. Good agreement is found between the measured data and theoretical calculations, when taking into account the specific flow conditions. The data highlight the significance of deactivation processes and the strong iodine repuniping mechanism within the cavity.For standard operating conditions a Rigrod type analysis reveals a small signal gain that is nearly constant throughout the cavity exceeding 1 .3% cm1 . The outcoupling reflectivity for the maxiinuni power output was found at a value of about 94%. These experimental data agree well with a simplified analytic model for gain saturation and power extraction as derived by G.D.Hager et al..

Unstable resonator with high magnification and low output coupling

“…The experiments have been performed with a chemical oxygen iodine laser (COIL) of the multi kW class 16 . The laser gas is expanded by supersonic nozzles into a channel of rectangular geometry.…”

Singlet oxygen generators - the heart of chemical oxygen iodine lasers: past, present, and future

“…Since the rotating disk generator's invention, research groups in such diverse countries as the United States [25][26][27], Germany [28], China [29], and India [30] have built lasers using them. The typical performance of the rotating disk generator is a yield of 40-50% with a utilization of 90% or better as shown in Table 2.…”

Recent results of iodine and water diagnostics in supersonic COIL

“…The BHP temperature near the disk pack changes slightly, while the gas temperature at the generator exit look very similar to Figure 7. The standard expression9 PH2O 10aT1+b+cT+dT2 (5) with a = 9.76K, b = -2755.53, c = -8.41 x 103K' and d = 5.53 x 106K2 is valid for pure water which has reached a themodynamical equilibrium between liquid and gas phase. In case of COIL, we use this formula for BHP.…”

“…From energy balances it has been estimated that a condensation of smaller amounts of water could be responsible for relatively high cavity temperatures in DLR COIL. 5 The availability of powerful scanning laser diode systems in the near infrared allowed the development of diagnostic tools for determination of ground-state oxygen O2(), H20 and iodine atoms I(2P112) [6]. All these tools, based on absorption spectroscopy, result in concentration values and temperatures from the recorded absorption lineshapes.…”