Description
Key Technical Specifications
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Model Number: ZMI 7714
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Manufacturer: ZYGO Corporation (USA)
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Laser Type: Helium-Neon, dual-frequency, internal Bragg cell
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Wavelength: 632.8 nm
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Output Power: 1.35 mW (nominal)
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Beam Diameter: 6 mm (standard) or 8 mm (option)
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Split Frequency: 20 MHz ± 1.6 kHz
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Frequency Stability: < 1 × 10⁻⁷ (1 s Allan deviation)
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Beam Isolation: Internal 30 dB optical isolator (back-reflection protection)
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Life Expectancy: > 20 000 h mean-time-between-replacement
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Cooling: Air-cooled (standard) or external water-cooled head for highest stability
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Operating Temperature: –40 °C…+70 °C head; 15-30 °C for best stability
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Power Input: ±15 V & +5 V DC from ZMI electronics rack (100-240 VAC supply)
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Interfaces: RF pick-off for heterodyne beat, interlock, temperature monitor
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Dimensions / Weight: Head ≈ 320 × 260 × 100 mm, 5 kg; electronics 19-inch 2U rack
ZYGO ZMI 7714
Field Application & Problem Solved
Semiconductor steppers need sub-nanometer stage feedback while the floor is vibrating at 50 Hz. Bolt the ZMI 7714 to the frame, run the 6 mm beam through a double-pass interferometer, and the 20 MHz beat gives you 0.31 nm resolution at 2.55 m/s with the ZMI 4104 board. I’ve used these on 300 mm wafer scanners—one laser feeds four axes, stays locked during a 0.5 g earthquake, and drifts < 5 nm over an eight-hour shift. Core value: it collapses a frequency-stabilized source, optical isolator, and RF driver into one head that you can swap without re-aligning the entire metrology path.
Semiconductor steppers need sub-nanometer stage feedback while the floor is vibrating at 50 Hz. Bolt the ZMI 7714 to the frame, run the 6 mm beam through a double-pass interferometer, and the 20 MHz beat gives you 0.31 nm resolution at 2.55 m/s with the ZMI 4104 board. I’ve used these on 300 mm wafer scanners—one laser feeds four axes, stays locked during a 0.5 g earthquake, and drifts < 5 nm over an eight-hour shift. Core value: it collapses a frequency-stabilized source, optical isolator, and RF driver into one head that you can swap without re-aligning the entire metrology path.
Installation & Maintenance Pitfalls (Expert Tips)
Water-cooling loop must stay above dew-point – Drop head temp below 18 °C in Singapore humidity and condensation pits the cavity mirrors; hold 22 °C ± 0.1 °C with facility water above 20 °C.
RF pick-off cable length is critical – The 20 MHz beat rides on a 50 Ω coax; add 2 m extra and phase shift gives false 0.1 nm steps. Use the supplied 1 m cable or trim to match the original length exactly.
Beam height tolerance ±1 mm – The isolator is wedged; tilt the head > 1° and back-reflection walks off the cavity, killing frequency stability. Shim the mount, don’t crank the bolts.
Ignore the 20 000 h hour-counter at your peril – Output drops 20 % at end-of-life; the ZMI board compensates until 0.8 mW then throws “Laser Low”. Log hours in the CMMS and order the spare at 18 000 h or you’ll discover the weakness during a production lot.
Water-cooling loop must stay above dew-point – Drop head temp below 18 °C in Singapore humidity and condensation pits the cavity mirrors; hold 22 °C ± 0.1 °C with facility water above 20 °C.
RF pick-off cable length is critical – The 20 MHz beat rides on a 50 Ω coax; add 2 m extra and phase shift gives false 0.1 nm steps. Use the supplied 1 m cable or trim to match the original length exactly.
Beam height tolerance ±1 mm – The isolator is wedged; tilt the head > 1° and back-reflection walks off the cavity, killing frequency stability. Shim the mount, don’t crank the bolts.
Ignore the 20 000 h hour-counter at your peril – Output drops 20 % at end-of-life; the ZMI board compensates until 0.8 mW then throws “Laser Low”. Log hours in the CMMS and order the spare at 18 000 h or you’ll discover the weakness during a production lot.
ZYGO ZMI 7714
Technical Deep Dive & Overview
The ZMI 7714 is a dual-frequency He-Ne laser head. An internal Bragg cell splits the 632.8 nm line into two orthogonally-polarized frequencies 20 MHz apart. A corner-cube cavity and active heater loop hold the cavity length to < 0.1 µm, giving frequency stability of 1 × 10⁻⁷. The isolator prevents back-reflection from the interferometer from pulling the cavity; the RF pick-off mixes the two beams and delivers the 20 MHz heterodyne signal to the ZMI electronics. Water-cooling removes ~30 W of waste heat, keeping the head within ±0.01 °C for ultimate stability. No user adjustments—just ±15 V and +5 V and the beat is present; lose any supply and the interlock kills the laser tube in < 1 ms to save mirror coatings.
The ZMI 7714 is a dual-frequency He-Ne laser head. An internal Bragg cell splits the 632.8 nm line into two orthogonally-polarized frequencies 20 MHz apart. A corner-cube cavity and active heater loop hold the cavity length to < 0.1 µm, giving frequency stability of 1 × 10⁻⁷. The isolator prevents back-reflection from the interferometer from pulling the cavity; the RF pick-off mixes the two beams and delivers the 20 MHz heterodyne signal to the ZMI electronics. Water-cooling removes ~30 W of waste heat, keeping the head within ±0.01 °C for ultimate stability. No user adjustments—just ±15 V and +5 V and the beat is present; lose any supply and the interlock kills the laser tube in < 1 ms to save mirror coatings.
