Modular 5 × 300 W diode laser heated FZ furnace with rectangular beam profile and advanced high-pressure process gas management

The main part of our laser-heated floating zone crystal growth furnace LKZ are five 300 W diode lasers with wavelength of 980 nm. The rectangular geometry and size of the laser beams which impact the sample can be changed in a wide range in order to adapt to different sample materials and rod diameters. Beside the configurable laser heating system, one of the most striking features of our LKZ furnace is the possibility to perform laser-heated FZ crystal growths at high gas pressure of up to 300 bar. There are LKZ versions with 10 bar, 50 bar, 150 bar and 300 bar max. pressure available. The composition and pressure of the process atmosphere can be adjusted and controlled precisely with independent mass flow controllers for each gas and an easily automatable pressure regulator. This worldwide unique set-up allows the user to control the elements diffusion between melt and atmosphere to a certain grade and to manage the growth of materials, which are difficult or impossible to produce at low gas pressures due to the higher volatility of their elements or a meta-stable nature of the desired phase. Our patented laser-based afterheater system provides unparalleled flexibility for conducting additional thermal treatments on samples. The vacuum turbo pump is connected directly to the process chamber using short and wide-diameter pipes. This ensures good vacuum inside the process chamber, even below 10^-5 mbar is possible. A lot of processes require an inert atmosphere with a low partial pressure of oxygen in order to perform ultra-clean growths. Our optional gas cleaning system removes oxygen traces out of argon reliably down to 10^-12 ppm residual O2 concentration.

Laser heating

• Standard configuration: 5 x 300 W (total 1.5 kW) diode lasers for homogeneous radial power distribution
• Laser wavelength 980 nm
• Laser beam geometry: rectangular beam profile with 4 x 4 and 4 x 8 mm (other beam sizes and geometries available on request)
• Step-less power control, melting temperatures between 300 °C and 3000 °C (material dependent)
• High power uniformity within the laser beam spot due to optimized optical components

Atmosphere

• Argon and oxygen (pure and in any mixture)
• Many other gases are also possible
• Gas pressure inside the growth chamber: 10^-5 mbar to 300 bar
• Manually controlled gas flow 0.1 to 1 l/min
• Each gas adjustable individually and independently

Pulling drives

• Precise linear and rotation feed through systems
• Pulling rate: 0.1 mm/h to 200 mm/h
• Fast gear mode
• Pulling length (max. crystal length): 100 mm (150 mm on request)
• Rotation rate: 0 to 70 rpm

Process control

• High-resolution CCD camera with HDR image optimization
• 360° image stacking system with 3 or 5 circularly arranged cameras available
• Precise two-color pyrometer for real-time temperature measurement
• Monitoring software: visual control, video recordings, snapshots, and length measurements during the process
• Several advanced power ramp and travelling ramp functions adaptable
• Comfortable GUI for all PLC-based adjustments

Required lab connections

• Gas supply with 12 bar pressure
• Exhaust air system
• Energy supply

Furnace dimensions

• Height: 3020 mm, width: 1630 mm, depth: 800 mm
• All components are integrated into the housing (electronics, laser power supply, gas management)
• Modular housing in the 4-laser setup available to meet space requirement for beamline experiments