Aiming to realize rough crystals of the highest Q value in the world

The previous story focused on our initiative to develop ultra-high-purity synthetic quartz crystals with a Q value of 4.3 million. We are about to launch a project to achieve ever higher purity. This story features our persistent challenge to realize rough crystals of the highest Q value in the world.

Development of synthetic quartz crystals whose Q value is 4.5 million or more

By using a growing furnace which enables precise temperature control and a high-purity raw material, we succeeded in growing ultra-high-purity synthetic quartz crystals whose Q value is 4.3 million, with about 1/100 of the impurities of conventional synthetic quartz crystals. What can we do to further enhance purity? We focused on the temperature and pressure of the growing furnace.

1️⃣ Reduction of the growth speed by attaining ultra-high temperature
In growing synthetic quartz crystals, the faster the growth speed, the more likely they will contain atomic clusters. This results in an irregular quartz crystal arrangement, and impurities are likely to enter the gaps, causing the Q value to decrease. When the temperature in the growing furnace is increased, the growth speed ratio changes on each axis of the quartz crystal, making it possible to reduce the growth speed compared to the ordinary process. Reduction in the growth speed causes atoms to be arranged regularly, making it difficult for impurities to enter. This helps increase the Q value.

At normal temperature Q value: 4.3 million When the growth speed is high, atomic clusters adhere, resulting in an irregular arrangement. Impurities are likely to enter the gaps, causing the Q value to decrease.

At ultra-high temperature Q value: ≥ 4.5 million When the growth speed is reduced at ultra-high temperature, atoms are regularly arranged, making it difficult for impurities to enter. The Q value can be further increased.

⇒ Crystals free from impurities can be created
by further reducing the growth in the thickness direction.

2️⃣ Atomic arrangement control at ultra-high pressure
In addition to reducing the growth speed at ultra-high temperature, we expect that the atomic arrangement can become closer to the ideal condition by increasing the pressure compared to the ordinary process.

At normal temperature Q value: 4.3 million

At ultra-high pressure Q value: ≥ 4.5 million

⇒ With the growth speed reduced at ultra-high temperature, the condition becomes closer
to the ideal condition at ultra-high pressure, leading to a higher Q value.

To realize 1️⃣ and 2️⃣, we are planning to introduce a growing furnace which can withstand ultra-high temperature and high pressure. Ultra-high-purity synthetic quartz crystals whose Q value is 4.5 million or more are expected to improve reliability in space development applications and to be applied to highly efficient laser beam conversion devices.

【Advantages in applications for space development】

Damage starts from an impurity/defect, causing the characteristics of a quartz crystal device to change.

Damage does not start from an impurity/defect. Thus, the characteristics of a quartz crystal device remain unchanged.

⇒ Reliability improves in applications for space development.

【Challenge in applying to a laser beam conversion device】

⇒ Highly efficient conversion into a laser beam suitable for microfabrication.