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Related Concept Videos

Effects of feedback01:24

Effects of feedback

Feedback in control systems plays a critical role in shaping various operational parameters, extending beyond simple error reduction to influence stability, bandwidth, gain, impedance, and sensitivity. Understanding these effects requires examining a basic feedback system characterized by defined input, output, error, and feedback signals.
Feedback significantly modifies the gain of a control system. The gain of a system without feedback is altered by a factor of one plus GH, where G represents...
Root Loci for Positive-Feedback Systems01:23

Root Loci for Positive-Feedback Systems

The Hartley oscillator is a positive feedback system that sustains oscillations by feeding the output back to the input in phase, thereby reinforcing the signal. Positive feedback systems can be viewed as negative feedback systems with inverted feedback signals. In these systems, the root locus encompasses all points on the s-plane where the angle of the system transfer function equals 360 degrees.
The construction rules for the root locus in positive feedback systems are similar to those in...
Parallel Resonance01:23

Parallel Resonance

The parallel RLC circuit is an arrangement where the resistor (R), inductor (L), and capacitor (C) are all connected to the same nodes and, as a result, share the same voltage across them. The parallel RLC circuit is analyzed in terms of admittance (Y), which reflects the ease with which current can flow. The admittance is given by:
Design Example: Underdamped Parallel RLC Circuit01:17

Design Example: Underdamped Parallel RLC Circuit

Consider designing an oscillator circuit, a crucial component in various electronic devices and systems. The objective is to create an oscillator circuit with specific characteristics: a damped natural frequency of 4 kHz and a damping factor of 4 radians per second. To accomplish this, a parallel RLC circuit is employed, known for its ability to sustain oscillations at a resonant frequency. In this case, the damping factor is pivotal in achieving the desired performance.
Starting with a fixed...
Sound Waves: Resonance01:14

Sound Waves: Resonance

Resonance is produced depending on the boundary conditions imposed on a wave. Resonance can be produced in a string under tension with symmetrical boundary conditions (i.e., has a node at each end). A node is defined as a fixed point where the string does not move. The symmetrical boundary conditions result in some frequencies resonating and producing standing waves, while other frequencies interfere destructively. Sound waves can resonate in a hollow tube, and the frequencies of the sound...
Oscillations In An LC Circuit01:30

Oscillations In An LC Circuit

An idealized LC circuit of zero resistance can oscillate without any source of emf by shifting the energy stored in the circuit between the electric and magnetic fields. In such an LC circuit, if the capacitor contains a charge q before the switch is closed, then all the energy of the circuit is initially stored in the electric field of the capacitor. This energy is given by

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Extra-cavity feedback into unstable resonators.

P B Corkum, H A Baldis

    Applied Optics
    |March 10, 2010
    PubMed
    Summary
    This summary is machine-generated.

    Unstable resonators are highly sensitive to external feedback. Even minimal reflected laser output significantly disrupts the temporal output of a mode-locked carbon dioxide (CO2) laser system.

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    Area of Science:

    • Optics and Photonics
    • Laser Physics
    • Nonlinear Optics

    Background:

    • Unstable resonators are crucial components in high-power laser systems.
    • External optical feedback can destabilize laser operation.
    • Understanding feedback effects is essential for laser design and stability.

    Purpose of the Study:

    • To experimentally demonstrate the sensitivity of unstable resonators to extra-cavity feedback.
    • To quantify the impact of attenuated feedback on laser output characteristics.
    • To develop a theoretical model for extra-cavity feedback in the geometric limit.

    Main Methods:

    • Utilizing a mode-locked transversely excited atmospheric (TEA) carbon dioxide (CO2) laser with a confocal unstable resonator.
    • Attenuating the laser output by approximately 10^6.
    • Reflecting the attenuated output back into the laser resonator to observe feedback effects.

    Main Results:

    • Significant perturbations (greater than or similar to 10%) were observed in the temporal characteristics of the output pulse train.
    • The experimental results confirm the high sensitivity of unstable resonators to even minute levels of extra-cavity feedback.
    • A theoretical framework was developed to explain feedback phenomena in the geometric optics limit.

    Conclusions:

    • Extra-cavity feedback poses a significant challenge for the stability of unstable resonators.
    • Precise control over optical feedback is critical for maintaining stable and predictable laser performance.
    • The presented theory provides valuable insights for mitigating feedback effects in laser resonator design.