Tsukuba Team Renders Mid-Air Plasma Holograms via Femtosecond Lasers

Yoichi Ochiai

Switching from nanosecond to ultrafast femtosecond pulses eliminates thermal and acoustic hazards, enabling touchable aerial plasma displays for everyday environments.

AI-assisted summary of Fairy Lights in Femtoseconds: Tangible Holographic Plasma (SIGGRAPH) — original source. Check the original for full context.

Source published: 2015-06-22

Key ideas

Researchers demonstrated 'Fairy Lights in Femtoseconds', an aerial and volumetric display system that renders true 3D graphics in mid-air using focused femtosecond laser pulses without screens, mist, or fog. (0:08)
Transitioning from nanosecond to ultrafast femtosecond pulses significantly reduces acoustic shock and thermal damage, producing a safer, quieter plasma capable of tangible interaction. (0:08)
The optical setup integrates a spatial light modulator (SLM) to dynamically adjust phase profiles and interference, rendering complex 3D holographic fields directly in ambient air. (1:10)
The experimental workspace occupies a 1 cm³ volume and supports spatiotemporal resolutions ranging from 4,000 up to 200,000 dots per second depending on the laser source used.

Detailed notes

## Background This video was published on YouTube by Yoichi Ochiai on June 22, 2015, presenting research conducted in collaboration with researchers from the University of Tsukuba, Utsunomiya University, Nagoya Institute of Technology, The University of Tokyo, and Sony CSL for ACM SIGGRAPH 2015. According to the description, it introduces "Fairy Lights in Femtoseconds," a method for rendering aerial and volumetric graphics in mid-air using focused femtosecond lasers and computational holographic fields.

## TL;DR The presentation demonstrates a system that projects aerial 3D graphics by exciting ambient air into laser-induced plasma without screens, fog, or physical matter. By transitioning from traditional nanosecond lasers to femtosecond pulses, the technology substantially reduces acoustic noise and physical danger, making plasma interaction safer for humans. Using spatial light modulators (SLMs) to sculpt computational holographic fields, the platform generates complex volumetric light points. The research establishes foundational optical principles, hardware setups, safety assessments, and scalability frameworks to bring tangible plasma-based volumetric displays into everyday interactive environments.

## Atmosphere & style The presentation carries a precise, serene, and academic tone, balancing rigorous optical physics with a sense of futuristic wonder. The narration is measured and objective, calmly detailing laser breakdown thresholds and spatial light modulation while tiny points of luminous plasma sparkle silently in mid-air. Watching the demonstrations feels almost surreal, as the quiet, glowing aerial forms replace the loud, concussive bursts historically associated with laser-induced breakdown, conveying a calm and calculated leap toward tangible science fiction.

## Bulletin - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) Researchers demonstrated 'Fairy Lights in Femtoseconds', an aerial and volumetric display system that renders true 3D graphics in mid-air using focused femtosecond laser pulses without screens, mist, or fog. - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) Transitioning from nanosecond to ultrafast femtosecond pulses significantly reduces acoustic shock and thermal damage, producing a safer, quieter plasma capable of tangible interaction. - [01:10](https://www.youtube.com/watch?v=AoWi10YVmfE&t=70s) The optical setup integrates a spatial light modulator (SLM) to dynamically adjust phase profiles and interference, rendering complex 3D holographic fields directly in ambient air. - The experimental workspace occupies a 1 cm³ volume and supports spatiotemporal resolutions ranging from 4,000 up to 200,000 dots per second depending on the laser source used.

## Key takeaways - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) 'Fairy Lights in Femtoseconds' renders aerial and volumetric graphics directly into ambient air without requiring physical projection substrates, fog, or screens. - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) The system excites ambient air molecules at precise 3D coordinates using high-intensity focused laser energy to generate visible laser-induced plasma. - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) Ultrafast femtosecond pulses yield plasma discharges that are significantly quieter and safer than previous nanosecond laser-induced breakdown methods. - [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) The dramatic reduction in thermal and acoustic hazard enables tangible, touchable volumetric graphics suitable for daily life and interactive applications. - [01:10](https://www.youtube.com/watch?v=AoWi10YVmfE&t=70s) Holographic graphics generation relies on a Spatial Light Modulator (SLM) to dynamically alter laser beam phase profiles via optical interference. - [01:10](https://www.youtube.com/watch?v=AoWi10YVmfE&t=70s) Computational holographic field control allows for complex spatial light distribution instead of relying solely on sequential mechanical beam steering. - Tested laser sources included a 30-100 fs laser firing up to 1,000 pulses/sec at 7 mJ and a 269 fs laser firing up to 200,000 pulses/sec at 50 µJ. - The system verified volumetric rendering spatiotemporal resolutions reaching 4,000 and 200,000 dots per second across the respective laser configurations. - The operational workspace and holograms occupy up to 1 cm³, with potential for scaling depending on optical devices and setup configurations. - The underlying principles extend beyond air plasma to other physical rendering media, such as fluorescence and microbubbles in solid or liquid materials. - [01:10](https://www.youtube.com/watch?v=AoWi10YVmfE&t=70s) The study defines an experimental and theoretical design framework addressing laser breakdown thresholds, safety margins, and scalability for plasma-based 3D displays.

## Detailed walkthrough ### [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) Aerial Graphics and Quieter, Safer Femtosecond Laser Plasma

The project introduces *Fairy Lights in Femtoseconds*, a rendering technique designed to cast aerial and volumetric graphics directly into the air using focused femtosecond lasers paired with computational holographic fields. By concentrating high-intensity laser energy at precise three-dimensional coordinates, the system excites ambient air to produce laser-induced plasma. This plasma emits visible points of light in mid-air completely free of physical screens, fog, or external projection matter.

A central motivation for shifting from traditional nanosecond lasers to femtosecond pulses is human safety and environmental impact. Because femtosecond pulses deliver energy over extraordinarily brief timeframes, the resulting plasma discharge creates a substantially safer and quieter physical interaction. The narrator notes the practical promise of this shift, explaining, “Daily life applications can be explored because plasma induced by a femtosecond laser is quieter and safer than that by a nanosecond laser.” This reduction in thermal and acoustic shock makes interactive, tangible mid-air plasma displays viable for real-world user environments.

```mermaid flowchart LR accTitle: Femtosecond Laser Aerial Plasma Rendering accDescr: Diagram illustrating how computational holographic fields and femtosecond laser pulses generate safe aerial plasma graphics in ambient air.

subgraph OpticalControl ["Holographic Control"] SLM["Spatial Light Modulator (SLM)"] -->|"Phase modulation & interference"| FocusedBeam["Focused Femtosecond Laser"] end

subgraph Emission ["Air Breakdown"] FocusedBeam -->|"Focal excitation"| Plasma["Laser-Induced Plasma"] Plasma --> Display["Volumetric Aerial Graphics"] end ```

- Aerial volumetric graphics are rendered in open air without requiring physical projection substrates or matter. - Plasma generation utilizing femtosecond lasers significantly lowers acoustic noise and physical danger compared to previous nanosecond laser-induced breakdown systems.

[01:10](https://www.youtube.com/watch?v=AoWi10YVmfE&t=70s) Spatial Light Modulation and Roadmap for Tangible Volumetric Displays

To manipulate light across three-dimensional coordinates, the optical engine incorporates a spatial light modulator (SLM). The SLM dynamically shifts the phase profiles of the incoming laser beams, leveraging optical interference to distribute light into complex spatial patterns rather than relying solely on sequential mechanical steering. As the narrator explains, “Our results led to calmer and safer plasma generation that can be incorporated into our daily lives.” This integration allows the system to achieve safe, high-resolution, and geometrically diverse volumetric graphics suitable for interactive displays.

The presentation also outlines the systematic design framework and experimental evaluation of the technology:

1. **Principles and Design Parameters**: Establishing the fundamental optical physics, breakdown thresholds, and spatiotemporal constraints governing femtosecond laser-based volumetric displays. 2. **Experimental Setup**: Introducing the engineered optical assembly, including the SLM phase-modulation architecture and beam path. 3. **Application Scenarios**: Exploring tangible 3D display concepts and direct user interaction spaces. 4. **Validation and Scalability**: Conducting detailed experiments evaluating plasma generation fidelity, human safety margins, laser beam control, operational limitations, and volumetric scalability.

Reflecting on the contribution to interactive graphics, the narrator emphasizes, “We believe that this study fills the gaps in design space of plasma-based 3D displays that were left unresolved by previous studies.” By combining computational holography with ultrafast laser pulses, the system establishes a new baseline for rendering touchable volumetric interfaces in everyday environments.

## Notable quotes > [00:08](https://www.youtube.com/watch?v=AoWi10YVmfE&t=8s) Daily life applications can be explored because plasma induced by a femtosecond laser is quieter and safer than that by a nanosecond laser.

## Mentioned Yoichi Ochiai, Kota Kumagai, Takayuki Hoshi, Jun Rekimoto, Satoshi Hasegawa, Yoshio Hayasaki, University of Tsukuba, Utsunomiya University, Nagoya Institute of Technology, The University of Tokyo, Sony CSL, ACM SIGGRAPH 2015, Spatial Light Modulator (SLM)

## Video description Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields Yoichi Ochiai*, Kota Kumagai**, Takayuki Hoshi***, Jun Rekimoto****, Satoshi Hasegawa**, and Yoshio Hayasaki** *University of Tsukuba ** Utsunomiya University ***Nagoya Institute of Technology **** The University of Tokyo and Sony CSL

project page: http://digitalnature.slis.tsukuba.ac.jp/2015/06/fairy-lights-in-femtoseconds/

Abstract We present a method of rendering aerial and volumetric graphics using femtosecond lasers. A high-intensity laser excites a physical matter to emit light at an arbitrary 3D position. Popular applications can then be explored especially since plasma induced by a femtosecond laser is safer than that generated by a nanosecond laser. There are two methods of rendering graphics with a femtosecond laser in air: Producing holograms using spatial light modulation technology, and scanning of a laser beam by a galvano mirror. The holograms and workspace of the system proposed here occupy a volume of up to 1 cm^3; however, this size is scalable depending on the optical devices and their setup. This paper provides details of the principles, system setup, and experimental evaluation, and discussions on scalability, design space, and applications of this system. We tested two laser sources: an adjustable (30-100 fs) laser which projects up to 1,000 pulses per second at energy up to 7 mJ per pulse, and a 269-fs laser which projects up to 200,000 pulses per second at an energy up to 50 ¹J per pulse. We confirmed that the spatiotemporal resolution of volumetric displays, implemented with these laser sources, is 4,000 and 200,000 dots per second. Although we focus on laser-induced plasma in air, the discussion presented here is also applicable to other rendering principles such as fluorescence and microbubble in solid/liquid materials.

Yoichi Ochiai, Kota Kumagai, Takayuki Hoshi, Jun Rekimoto, Satoshi Hasegawa, Yoshio Hayasaki, Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields, http://arxiv.org/abs/1506.06668　(ArXiv Preprint: *Submitted to ACM Transactions on Graphics (via Acceptance with major revision in ACM SIGGRAPH 2015)

Yoichi Ochiai, Kota Kumagai, Takayuki Hoshi, Jun Rekimoto, Satoshi Hasegawa, and Yoshio Hayasaki: Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields, Proc. ACM SIGGRAPH 2015, Emerging Technologies, accepted, Los Angeles, California (USA), 9-13 Aug., 2015. [Demo]

Yoichi Ochiai, Kota Kumagai, Takayuki Hoshi, Jun Rekimoto, Satoshi Hasegawa, and Yoshio Hayasaki: Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields, Proc. ACM SIGGRAPH 2015, Posters, accepted, Los Angeles, California (USA), 9-13 Aug., 2015. [Poster]

Yoichi Ochiai, Kota Kumagai, Takayuki Hoshi, Jun Rekimoto, Satoshi Hasegawa, and Yoshio Hayasaki: Fairy Lights in Femtoseconds: Aerial and Volumetric Graphics Rendered by Focused Femtosecond Laser Combined with Computational Holographic Fields, Proc. ACM SIGGRAPH 2015, Talks, accepted, Los Angeles, California (USA), 9-13 Aug., 2015.

[Source](https://www.youtube.com/watch?v=AoWi10YVmfE)

中文简报

筑波团队利用飞秒激光实现空中等离子体全息投影从纳秒脉冲转向超快飞秒脉冲消除了热危害与声波危害，实现了适用于日常环境的可触控空中等离子体显示。该展示介绍了一种无需屏幕、雾气或实体介质，仅通过激发周围空气产生激光诱导等离子体来投影空中三维图形的系统。通过从传统的纳秒激光转向飞秒脉冲，该技术大幅降低了声学噪声和物理危险，使人与等离子体的交互更加安全。该平台利用空间光调制器（SLM）构建计算全息场，从而产生复杂的立体光点。这项研究确立了基础光学原理、硬件配置、安全评估和可扩展性框架，旨在将可触控的等离子体立体显示技术引入日常交互环境中。研究人员展示了名为“飞秒小精灵之光”（Fairy Lights in Femtoseconds）的空中立体显示系统，该系统利用聚焦飞秒激光脉冲在空中呈现真正的三维图形，无需屏幕、水雾或烟雾。 (0:08) 从纳秒脉冲过渡到超快飞秒脉冲显著减少了声冲击和热损伤，产生了更安全、更安静且能够进行实体触控交互的等离子体。 (0:08) 该光学装置集成了空间光调制器（SLM），可动态调节相位分布和干涉，直接在周围空气中呈现复杂的三维全息场。 (1:10) 实验工作空间体积为 1 立方厘米，根据所使用的激光源不同，可支持每秒 4,000 至高达 200,000 个点的时空分辨率。

Reading summary

The research project Fairy Lights in Femtoseconds, presented by Yoichi Ochiai, demonstrates a technique for generating screenless aerial volumetric graphics by exciting ambient air into laser-induced plasma using focused femtosecond lasers and computational holography. Femtosecond Lasers for Safer Aerial Plasma (0:08) The system renders mid-air volumetric graphics directly into ambient air without requiring screens, fog, or other physical projection media by focusing high-intensity laser energy to produce laser-induced plasma. Moving from conventional nanosecond lasers to ultrafast femtosecond pulses concentrates energy into brief intervals, which significantly reduces both acoustic shock and thermal danger during the plasma discharge. According to the researchers, this reduction in physical danger and noise makes plasma displays viable for everyday interactive environments. The narrator asserts that this calmer discharge allows practical daily life applications to be explored where previous laser-induced breakdown systems were too hazardous or disruptive. Spatial Light Modulation and Holographic Control (1:10) To render complex three-dimensional shapes without relying entirely on sequential mechanical beam steering, the optical architecture incorporates a spatial light modulator. The device dynamically adjusts the phase profiles of the incoming femtosecond laser beam, using optical interference to project energy across arbitrary three-dimensional coordinates to form high-resolution volumetric graphics. Design Framework and Experimental Validation (1:10) The project outlines a systematic engineering framework covering fundamental optical physics, air breakdown thresholds, and spatiotemporal operational constraints. The researchers evaluated the setup through experimental tests focused on beam path management, plasma rendering fidelity, human safety boundaries, and the physical scalability of the volumetric interaction space. The authors state that integrating computational holography with femtosecond lasers addresses unresolved design gaps in earlier plasma-based 3D displays, establishing a framework for touchable aerial interfaces while requiring further assessment of operational limitations and volumetric scalability.

精炼阅读摘要

落合阳一（Yoichi Ochiai）团队在SIGGRAPH上介绍了“飞秒光点”（Fairy Lights in Femtoseconds）技术，通过结合聚焦飞秒激光与计算全息空间光调制技术，在无需任何物理屏幕或介质的环境中激发出更安全、低噪音的空中可触控等离子体体积图像。飞秒激光激发空中等离子体与安全性提升 (0:08) 该系统利用聚焦飞秒激光的高强度能量精确作用于三维空间坐标，直接激发周围空气产生激光诱导等离子体，进而在半空中形成肉眼可见的发光点。整个呈现过程完全摆脱了传统投影所需的物理屏幕、雾气或其他外部投影介质。项目采用飞秒脉冲替代传统纳秒激光的核心动因在于降低对人体的危害与环境影响。飞秒脉冲在极短时间内释放能量，显著抑制了热效应与冲击波噪声。旁白指出，飞秒激光诱导的等离子体比纳秒激光更加安静和安全，从而为等离子体交互显示技术进入日常生活应用场景提供了实际可行性。空间光调制器驱动的计算全息光路控制 (1:10) 在光路操纵方面，光学引擎集成了空间光调制器（SLM）。该器件能够动态改变入射激光束的相位分布，通过光学干涉原理将光线投射至复杂的三维空间结构中，而非单纯依赖传统的机械偏转装置。研发团队认为，这种全息调制方式带来了更稳定、平缓且安全的等离子体生成效果。通过结合计算全息与超快激光控制，系统能够在保障人身安全裕度的前提下，生成高分辨率且具有几何多样性的空中三维图像。系统设计框架与可触控体积显示验证 (1:10) 该研究建立了一套完整的工程框架与实验评估体系，涵盖光学击穿阈值、时空约束条件等物理基础原理，并构建了包含SLM相位调制的光路工程实验装置。此外，团队系统评估了等离子体成像保真度、人体接触安全边界、光束操控能力以及体积缩放限制。研究者强调，该工作填补了以往等离子体三维显示研究在设计空间上的空白，为开发适用于日常交互环境的可触控三维界面奠定了技术基础。该研究通过飞秒激光与计算全息的融合，有效克服了传统纳秒激光等离子体的高噪声和高危险性缺陷，但在走向日常实际应用的过程中，仍需进一步围绕激光光束控制、显示体积扩展以及长期运行稳定性等局限展开深入验证。

Source quotes

[0:08] Daily life applications can be explored because plasma induced by a femtosecond laser is quieter and safer than that by a nanosecond laser.

Original transcript

[0:08] Very lights and femtoseconds. Aerial and [0:11] volumetric graphics rendered by focused [0:13] femtosecond laser combined with [0:15] computational holographic fields. [0:22] We present a method to render an aerial [0:24] and volumetric graphics in air by [0:26] femtosecond lasers. Laser-induced plasma [0:29] emits light without involving physical [0:31] matter. Daily life applications can be [0:33] explored because plasma induced by a [0:35] femtosecond laser is quieter and safer [0:37] than that by a nanosecond laser. [1:10] We use an optical device called the [1:12] spatial light modulator to modify the [1:14] phases of light rays and produce various [1:16] spatial distributions of light based on [1:18] interference. Our results led to calmer [1:20] and safer plasma generation that can be [1:23] incorporated into our daily lives. [1:31] The design space and possible scenarios [1:33] of the plasma-based 3D display are [1:35] discussed. [1:44] We explore a safe, high-resolution, [1:46] wide-variety laser-based volumetric [1:48] display using a femtosecond laser and an [1:51] SLM. [2:21] The remaining sections of this paper [2:23] discuss the following. First, we [2:25] describe the principles and design [2:26] parameters of femtosecond laser-based [2:28] volumetric displays. [2:45] Second, we introduce the setup we [2:47] designed. [2:51] Third, we give examples of applications. [2:53] Finally, we conduct experiments on [2:55] generation, safety, and control of [2:58] lasers. We also discuss the limitations [3:00] and estimate scalability. We believe [3:02] that this study fills the gaps in design [3:04] space of plasma-based 3D displays that [3:07] were left unresolved by previous [3:09] studies.